Cylinder melt down.

[Albatros]

Well, I put in a 70cc cylinder kit, carbon reeds, a RS Technigas pipe, a 19mm Arreche carb with the unifilter and, after I got it all installed, I got it running pretty descent and had the carb tuned in when it developed a bad knock in the crank case. I initially thought it was in the variator so I rode it down the street to see if the weights would spin out. Well, I got about 2/10 of a mile around the block and it was incredibly fast then it started sounding funny and ran slugish so I shut it down and pushed it home. This morning I pulled the cylinder and my piston was cooked and the cylinder was marred up and the piston ring was locked into the piston. So I switched back to the stock 50cc cylinder and still have the rest of the mods on it. Now I got it running and it sounded really good. It even starts easier than when new but the knocking is still there and seems to ge worse at idle and go away with acceleration. It was working perfect with the stock carb, pipe, and exhaust and the 70cc cylinder head If I could do it over I would go back to all stock and just upgrade the cylinder to the 70cc. It had nice acceleration and topped out at around 60 or so. It felt very stable with a nice reponsive throttle all the way from 0-60. Well, anybody had any experience with this kind of thing before I pull the engine and take the crank case apart to look for the knocking. I'm thinking maybe it is a bearing that has come loose. How I don't know. Well I guess I'll take it apart tonight and see what I can see. :(

Does anybody think it could have been any of the performance parts listed that could have caused this?

Once I figure out what went wrong I'll need a new 70cc cylinder. Should I get another Airsal or is there something that might hold up better?

[Zuma-Zuma]

It doesn't sound like you had much of a break-in. Sort of trial by fire. The motor melt down may have sent debris into the upper or lower crank bearing. OR you may have debris in the lower crankcase. Do you have any pics of the cylinder or piston? This would aid in the cause also. It is also possible that a screw from the reeds or other debris actually entered the motor. Pics help alot.

[Zuma_Man]

maybe this would be covered by the cylinder warranty?

[XPS1210]

I think the knocking was probably the variator, did it do it at idle or when at higher RPM's? Just my opinion...

if the 70cc kit was litterally melted, then you were lean on fuel or had no oil... did you hook up the oil line? Sure it was getting oil... there is no way if it was getting oil and fuel properly that it could possibly have destroyed the cylinder in 2/10's of a mile... simply couldn't do it...

[moosehead]

Once I didn't tighten my vari properly and it knocked and slipped. Running really fast then siezing sounds like a lean condition to me. Perhaps the pipe leaked at the cylinder or the carb was too lean. I'm guessing you used the 95 jet that came with the carb. That should have worked from what I've read

[Zuma-Zuma]

A backwards piston may do it. So would an air leak, no or lack of oil. Thats why I say pics will help. We can guess all day....

[Albatros]

O.K. here are some replies:

First of all,my cylinder didn't actually melt down. I almost did though.

Second of all I forgot something. I ran it on the initial test ride with the cooling fan removed as well as the engine cowling off.

Thirdly, I am open to the idea that the knocking may be totally unrelated to the piston problem and that if the knocking had not occured the piston might still have been damaged by heat. The wrist pin on the 70cc cylinder kit had the typical look of metal that has been over heated. The knocking may have been harmless and the piston may have just been run to hot due to being too lean or the missing cowling.

I'm not sure what you want a picture of. The cylinder is marred inside and the piston ring is fused into the piston. The cylinder is marred at a place that corresponds with the gap in the piston ring. One end of the piston ring is free and the other end is locked in tight. I haven't taken the rest apart yet so there is nothing else to see.

I added a little two stroke oil to the fuel to be safe about the oil pump not being primed and was getting smoke out the exhaust so I beleive it was getting oil.

The piston was put into the cylinder with the port on the piston skirt corresponding to the port on the cylinder and opposite the exhaust. The cylinder & head itself had about 250 miles on it with no problems so the cylinder kit was use to running in the 30-40mph range which is what I ran it at on the initial ride. When I say fast I mean to say it had awsome throttle response which I attributed to the larger carb, unifilter and RS pipe and carbon reeds.

I checked the carbon reeds (and switched back to the stainless with the stock cylinder) and reed block and all parts were accounted for.

The knocking goes away when the engine is reved and then the knocking comes back at idle.

The problem did start after I switched out the clutch springs and put in the variator. So I swithced the variator and clutch back to stock but the problem continued though it is not as loud.

I didn't see that any metal was missing from the cylinder or piston and the ring was in tact but could not be removed from the piston.

I used a universal rotor holder on the magneto fly wheel and had to torque like hell on the variator bolt to losten it. Has anyone heard of bearings in the crank case, or anything else for that matter, being damaged by removing the variator nut with force?

The engine now starts and runs perfect but I cant ride without fixing this knock. Nor will I start it again unless it is to try and find the source of the problem. But first I need to have a plausible source in mind, a way to test it, and a reasonable solution to curing the problem.

I was wondering about testing the variator. The engine can not be started without it in place so how do I isolate it in order to see if that is indeed the source of the knocking. The problem seems to occur at idle so could I pack it with something then remount it and see what happens?

[XPS1210]

Second of all I forgot something. I ran it on the initial test ride with the cooling fan removed as well as the engine cowling off.

The knocking goes away when the engine is reved and then the knocking comes back at idle.


here is what I have to say...

your mention on the fan being off and the plastic cowling... WTF were you thinking... you litterally rode it with no possible way to cool itself! and begged to have it destroy itself... If anyone else does this... WOW... that is the WORST POSSIBLE thing you could do!

the knocking deal... is the variator if it gets louder with idle and the more you rev it goes away... Mine did this till I added a HUGE washer to mine to make it all tight... it's from the variator moving around on the crank shaft... The washer I used is like 1/4 inch thick... and holds it all REAL tight the nut just fits on the shaft...

[Zuma-Zuma]

Can you start it with the tranny cover off? Then you can at least tell if its near the clutch or variator, and isolate from there. You can also start it without the belt, this will tell you which pulley the problem is coming from. You may want to change the spark plug, and see if that stops the knocking. Sometimes its a spark knock, rather than a mechanical knock.

[Albatros]

I know I screwed up and probably fried my cylinder due to a lack of cooling and brains. :angry:

So I can fix the cylinder problem with another 70cc cylinder and I will remember this forever. I forgot about the fan and cowling and just rememberd it this morning when I went out to take off the cylinder. I've had other air colled bikes that had no cowling and used only radiant heat loss for cooling and so I didn't think it would hurt it. I just need to know now that the rest of the engine is o.k. I'm sure Erich wouldn't mind me buying another Cylinder kit from him. Me being an idiot is gonna keep him doing business straight through to winter at the rate I'm going.

So where did you put the washer? Did you put it behind the starter disk or behind the variator plate?

[Albatros]

Hi Zuma-Zuma. Today I did start it with the cover off and the belt off too and I checked the spark plug. The noise is definately coming from near the variator. I think Jered is correct. The noise was worse with the new variator and quieted down with the stock one in its' place. As I'm sure you've already read, the engine melt down was due to my being a D.A. about the cowling and fan thing.

[XPS1210]

I think that your probably okay with the rest of the engine...

the question I have is: do you have access to a camera... ? What does the cylinder walls look like? If they are not scratched then erich can get you a new piston and rings instead of a whole cylinder kit... The pistons are something like $60 and rings $10 or something each... so if the cylinder is good just order the piston and rings... if the cylinder is scratched up too, then get a whole kit...

the reason IMO that you can't run the scooter without the fan and such... because the scooters motor is covered, unlike motorcycles that are exposed to the air and the air flows easily over it...

I put the washer after the finned pulley (and the star that fits in the finned pulley), then the large washed and then the kick start gear and the stock large washer and then the nut...

[moosehead]

When mine made this noise, I think it was because I didn't put the washer under the nut correctly. It is dished, and I had put it with the covex side facing the motor. Flipped it over and tightened it down, no problems now. Thinking that radiant cooling would be fine is not that dumb, at idle. Under power and load, there is no airflow over the motor. Not sure if the siezing could have happened in 2 blocks, but I don't trust nikasil, so it wouldn't surprise me.

[Albatros]

I'm thinking about going to cast iron with two rings. Erich dosen't sell them with a 12mm wrist pin though. Why don't you trust the aluminium with the nikasil coating?

[Albatros]

Zuma-Zuma,

After thoughtfull deliberation on my part, I felt it most prudent to post some pictures. If only to make the forum a more interesting place for those who have no I dea what the heck my screwed up engine destroying self is trying to say.

You can see the marring on the cylinder that corresponds perfectly to the damage to the piston when the piston is inserted as it would be when attached to the small end of the connecting rod.

Next are a couple pics of the piston and the fused ring. One edge is actually free and prodrudes from the piston slightly.

The second to last pic is of the wrist pin. It's burnt. And that's all I got to say about that.

The last pic is of my new RS pipe. It just looked cool.

[moosehead]

Wow, total devistation. My condolences. Definitely overheated and siezed.
I don't trust Nikasil because, in addition to being an engineer, I am a BMW mechanic. Starting in the mid 90s, All BMW V8s were Nikasil. Almost all of them got 1 or 2 replacement motors until the problem was fixed in 96 with Alusil motors. These motors wear the cylinder walls and lose compression. I don't trust Nikasil to take the abuse that cast iron has for decades. The cast block/aluminum heads have proven themselves to be 300k+ mile engines in BMWs and Benzes, while the aluminum engines are usually gone by 150k.

[XPS1210]

I'm not sure what to say...

here is what I see, horrible blow by, probably caused from the over heating and damage to the ring...

It looks like you have only scratching on the side right where the blow by is... which makes me wonder... is the scoring you have from the hot gases blowing past the ring? and being the caused from lack of lube or something... I can't say on that one... as that looks like a piston that has been ran a while... not just 2/10's of a mile... normally you don't see that much damage...

so I'm not sure of exact cause from looking at it... http://www.provoscooter.com/vbull/article.php?a=51 here is a "guide" to what damage you have on your piston to tell you what is wrong... maybe you can see it better from having the piston...

[Albatros]

The plot thickens. Under the intake seizure it says water in the fuel system....hmmm I actually had to drain the gas and replace it with new stuff cause I noticed the gas I was using when all this happened was causing a lot of water in the exhaust. Actually this morning the thing wouldn't start at all until I got the gas drained out and replaced. I wonder if it wasn,t a combo whamy. A little lean cause I was still adjusting the carb, no cowling and fan, and water in the fuel hitting the intake area of the piston spraying the oil off instead of coating it. The plug this morning actually had water on it before I chandged the fuel.

Thanks for the link that helped a lot.

[Albatros]

Oh and I have the black spot under the crown of the piston behind the wrist pin to. It looks just like the picture. The cylinder and piston had a couple hundred miles on them so there was a little carbon on the kit from that but the scratching is definately new.

I used high octane gas that was new. I wounder if humidity in the ambient air could have been pulled into the carb. But then again I noticed when I got it running today that condensation was on the outside of the carb and it was rainy and foggy just like last night and yet with the new gas the bike seemed to run fine.

And it sounds like maybe I better go with a cast iron head. I wonder if Erich can order one for me with a 12mm wrist pin. I'm not sure if the Airsal was given a fighting chance but I don't really have the capitol to give it a second one either. Sounds like a good post topic. Aluminium vs Cast Iron.

[XPS1210]

erich already posted this... look at the sales page www.provoscooter.com and you can see the cast/aluminum

[Albatros]

I read the Aluminium vs. Cast Iron when I originally bought the stage two. I just didn't want to sacrifice performance for reliability as is often the trade off when going to modifications. The article states a lot about the cylinders being used in racing engines. Sponsers and promoters pay big money to have engines rebuilt after every race so wear and tear isn't as much an issue as short term performance. I just wondered if you couldn't get the performance out of the fact that it's a 70cc cylinder vs. the stock 50cc. And go with the cast iron for dependability. If the 70cc I have now was cast iron I might have been able to clean it up with a hone as it does not appear to be heat damaged. Though I guess it could be warped and I just can't appreciate it without a micrometer.

Maybe the Aluminum would still be alright to go with if I don't forget to put the fan and cowlings back on, run it a little rich and change the plugs every, and stick with the B.P. down the street when trying to purchase gas (instead of the spring water I purchased at Lou Perines Gas station on the corner of Sheridan Rd. and 52nd St. in Kenosha Wisconsin) _-_-_-

Hey...I got a question. The oil injector. It appears to be controlled by a seperate cable that is joined to the throttle at a junction box. It is all still hooked up and working fine. But my question is: does the amount of throttle applied simply activate the pump and cause it to inject a predetermined amount of oil, is the amount of oil based on engine rpms as the pump is driven directly by the crank shaft, and does the 70cc require more oil since the carb is now bigger and pushing in more fuel and with the pipe it allows the fuel to run through faster possibly not giving it enough time to pick up enough oil.

What is the standard mix for a 50cc Mineralli two stroke? I thought it was 5 ounces / gallon which is approximately 148 ml / gallon. I would guess the oil injector is set to compensate for this ratio with the stock carb and pipe and air filter regardless of engine speed yet this may be directly affected by fuel and air volume flow through the mod air filter,carb, and pipe.

Should I add oil to my gas to compensate or what?

[XPS1210]

Hey...I got a question. The oil injector. It appears to be controlled by a seperate cable that is joined to the throttle at a junction box. It is all still hooked up and working fine.

If your throttle is like the bug eye zuma, it's not a oil injection cable... the throttle is a push - pull system... not sure why they do that other then to eliminate free play in the throttle...

the oil injector on my zuma is mechanical and runs only off of engine RPM's... via a gear connected to the crankshaft... As far as I can guess from what you are saying is that your throttle cables are push - pull like the zuma... Can you see the carb? if so are there 2 cables leading to the top of it as I discribed the zuma being?

[Albatros]

No the vento Triton R4s aren't the push pull type. They have a single throttle cable that runs to a junction box that converts it into two cables the carb cable that controls the throttle slide and the injector cable that runs to the oil pump. I just rebuilt a Zuma Prebug and I know what you mean about the oil injector. The thing is behind the magneto and staters and the gears are under a plate and gasket and you have to remove the oil injector gears to change the oil seals and inspect the main bearings. I haven't broken into that part of the vento yet cause I haven't had a reason to.

I think when I get the new cylinder kit I wil just go to premix. Throw a couple of 5 ounce bottles of blue marble or Yamalube under the seat and add a gallon at a time. That doesn't sound to inconvenient. I wonder about the oil pump though. Could I just cap it or is it internally oiled as the lube passes through it. I know the drive mechanism is in a seperate compartment and is packed in grease on the Zuma Prebugs. I guess I'l have togo to the vento sight and try to make sence of their substandard blow up diagrams.

[XPS1210]

okay.. sorry... figured it was that way... that's odd to have it that way... I'd be scared the cable would break... my throttle cable broke on my zuma right before I changed everything back to stock... and what a pain... I had to pull the throttle cable by hand through the plastics... and it was hard as heck to pull... needless to say by time I rode the 3 miles home, I was pretty ticked off....

[speedy_scooter]

The Vento injector is adjustable. You back that nut off I'd say about 3-5 turns. That will give your bike more oil. I still add an ounce to the gas just to be safe but you can keep the stock injector.

[Albatros]

You know It looked adjustable, I just wasn't sure how it was calibrated to get the right fuel to oil mixture out of the thing. I've changed the engine back to the stock 50cc and it runs perfect. I checked the variator and it was the source of the noise as others have mentioned. I switched back to the stock variator for now. The rattle was just to much on the nerves for the time being. I also put about an ounce of oil in my fuel since I'm gonna go ahead and run the 19mm carb with the unifilter and the RS pipe until I order my new cylinder. But now I'm wondring how I can tell how much oil is the injector injecting with the factory pre-set, and how is it callibrted for adjusting purposes. I'll e-mail Vento and ask. They usually answer within 48 hours. I figure if I know the pre-set I can add the right amount of oil to my fuel to get the desired fuel to oil ratio. It is still a little scary to think that if the cable breaks but not the carb cable, I could possibly ride around with my oil injector not working and not know it till it's too late. I'm still leaning towards going to straight premix and disabling my injector. Changing engines is fun but a little expensive.

So this leads me to another question; does anybody know the recomended fuel to oil ratio for the Airsal T6 Aluminum Cylinder with a 19mm Carb, unifilter, and RS pipe. I think I'll post this as a seperate thread. I know it has probably been done before but opinions change and the archeves are a pain to run through some times.

[burnt_toast]

The variator has to break in then noise goes away and if you have the malossi, the washer placement is different. i learned this after the incorrect setup caused my stock belt to snap.

[speedy_scooter]

Just back off the screw about 3-4turns and you'll be fine. I am running my setup that way and I have plenty of oil going to my Corsa. I'd be surprised if the cable snapped, I havent heard of any cables snapping besides Jered's.

[Albatros]

I'll go out later and take a look at it. I want the fuel ratio thing settled and I want to put a couple hundred on the engine before I put in another 70cc. I'll try the adjustment and see how it rides.

[Albatros]

Thanks

[speedy_scooter]

What you could do is leave everything the way it is and do a plug check, then just turn out the oil adjuster 1turn ride it for 5miles or so then do a plug read again and see if its got more oil then before. It should be a darker plug.

[Albatros]

Update on the melted motor. I got bored so I went out to the garage and checked out the cylinder again. It didn't look to bad. So.........I hit the piston ring with a heat gun and it to unseat itself from the piston. Then I cleaned all the carbon off of everything and polished the cylinder, wrisp pin, piston, piston ring, and head with metal polish and a dremel buffing tool. It looks pretty good and the piston slides rite through the cylinder. It turned out so well that I'm thinking about trying it out and seeing what happens. I'm still gonna buy a new cylinder kit so either way I'm out about $190, but now I'm currious about seeing if this thing will run O.K. or blow up. Ah, WTF I might as well try it... I'm gonna figure out the fuel ratio thing then go try and blow up my scooter!

[Albatros]

I have to go to another birthday party at 1500 hrs or uhhhhh 3 pm I mean. Aren't kids great. I'll try to blow up my cylinder tonight when I get back or first thing in the morning. Here are some pics of what's going on the scoot. The first pick is the head after it was sanded clean of the burnt oil and carbon with 400 grit paper. The second is the same head after polishing. The carbon should find it a little harder to hang on now. the third is the "destroyed" cylinder kit after polishing. All surfaces got the treatment. The coating inside the cylinder seemed to polish well with no appreciable loss of material. I slid the piston through the cylinder in a position that should be close to where it will be when re-installed. The thing feels like it did when I played with it when it was brand new. :rolleyes:

[Albatros]

No real fire works but the official results are in. Compression is horrible making the thing extremely difficult to start and impossible to keep running. The head will be kept and the the head gasket as well. I'd send the cylinder back to Airsal for recoating but I think the damage is too bad. I don't trust the temper of the wrist pin but the retaining clips looked fine and work a lot better than the stock c clips so they are now currently back in the scooters stock 50cc and are working fine.

[ex-racer#2]

How much to nickasil? There is Millenium technolgies in the US do it but I am not sure if it will save over the cost of a new cylinder. Also a place in Quebec does it. Both have decent reputations and the guys in Quebec do nice work.

[Lennox]

I know on larger 3cylinder motors like waverunners replating saves a bunch. On these small motors, I would imagine it cost about as much as a new cylinder.

[Albatros]

After factoring in the cost of repair, the shipping and the run down to the UPS depot, though it would give me a reason to ride my scooter so I factored that as a pro instead of a con, I would still have a cylinder that had been heat stressed. I'm sure the factory boys would run a bore caliper through it and check for round, since the cylinder could very well be warped, and the coating would be like new, but it would still always make me wonder. Oh and the cost of the shipping and recoating is about the same cost as a new cylinder kit of the same brand.

I already ordered a new polini air cooled "evo" for $230 from Germany and it now sits in a customs clearing house in Philadelphia at the UPS Main Eastern Sea Board Hub. It should be here by monday. I may wait to put it on though.

I want to do some drawings and order a second air shroud and cowling and do a proto build of a hot air induction system to possibly help with generating a more consistant air temp in the induction manifold via the air filter from air routed up from the engine shroud. This should aid in quicker warm ups for winter and cold fall starting conditions and yet not change the uper temp the engine would reach. My only fear is fulling too much air of a localized part of the engine via the engine shroud and theoretically creating a cold spot on the cylinder wall. I have to check and see if there is enough surface are in the shroud at a reasonable distance from the cylinder to place the hot air itake. If what I'm 99% sure will happen, there will be no adverse affect on the cylinder and the system could be left in place year round. The benefit would be a bike that would warm up quicker regardless of ambient air temp. There should be no increase in the upper temperature range. This would not be a performance modification that would increase anyghing but reliability and decrease the possibility of damaging the engine due to riding before the engine is properly "warmed up".

The hot air induction system would also decrease the problem of condensation from ambient air humidity condensing on the colder surface of the internal carb body as the carb would be kept at a consistantly warmer temp. The overall ratio of oxygen to nitrogen found in the atmosphere may be affected by the excitation of the gas molecules. This oxygen excitation could decrease the ratio slightly but at an unappriciable level. It would be like riding your scoot in the summer rather than the winter. In the winter the air is denser. Less excitation due to decreased temperatur means the ambient or atmospehric air has more oxygen mollecules per liter of air flowing through the carb and into the combustion chamber. Humidity in the air also displaces oxygen per liter of air. This is why our scooters run very well on a cold day in fall with low humidity after the scooter has been warmed up. You simply have a greater concentration of oxygen and thus the scooter runs slightly lean.

The humidity would remain constant in the air fuel emulsification entering the actual air filter and carb body but the water molecules would tend to ramain in an excited or gasseous state and thus have less of a concetrated affect on the overall system.

On my current system, the carb gets cold, the cylinder gets hot and the exhaust gets really hot once the scooter is warmed up to its usual riding temperature. On auotomobiles, the hot air induction sytem pulls air off of the exhaust manifold through a metal shroud to more evenly heat the entire fuel induction system. The ideal system would pull the wasted radiant heat comming off the first 6-8 inches of the exhaust pipe and use it to heat a portion of the air going into the air filter. If all air going into the filter was first staged into a large air reservoir in which the cooler ambient air could be mixed thuroughly with the heated air the system would help create an evenly heated air fuel mixture entering the crank case thus increasing overall gas emulsification and making for a more homologous mixture as well.

So what do you think. Do I have too much time on my hands or what. I think I'll do some technical drawings and post them for review. It's cold outside and I have nothing to do until my new cylinder gets here.

[speedy_scooter]

I find that the stock cooling works very well. As long as your carb is tuned right then you dont run hot. And btw, have fun with that Evo and let us know how it turns out.

[Albatros]

It should be here by monday. If I keep my head out of my butt I should get it in without to much trouble. The rest of the scooter is ready to go. I ordered a set of clutch spring as well as the Evo. I think the clutch should be just a little tighter but other than that the thing should be a dream to ride. Though with the highs in the 40's I might have to wait till spring to get it ready to go. Oh who am I kidding I'd ride it in the snow to test it out if I had to.

My scooter runs at a nice temp now and the plug check looks good and the cylinder hasn't tried to melt on the 50cc so I think I am at a good jumping in point for the Evo.

My idea on the heat induction for the intake was spawn of boredom and the need to practice my typing skills. In theory I think it would work. But in theory, I thought my 70cc Airsal would work too and now it is a very interesting paper weight. So I think I'll look for a test engine or better yet, stick to drawings and discusions. yeah .... that sounds safer and cheaper.....