89' Zuma with @ speed issues

[DrDoom]

Hi all,

Ok, I got a 70cc kit, fitted fine, started fine. Acceleration is good, idles fine. But once I get going i cant maintain a high speed, i get to about 15mph and thats it. It will cough and splutter. I'm using the standard Y12P carbie with a bigger main jet. To say the least I'm getting mad as hell with it. :mad:

Any suggestions?

Cheers

[acekool]

I have 17mm Polini carb and intake on my 89. Also you need a performance pipe if you don't already have one.

[DrDoom]

I have 17mm Polini carb and intake on my 89. Also you need a performance pipe if you don't already have one.
No performance pipe as yet, but it should still go quicker than it is now.
If I need a new carb to make it run, i guess i'll have to get one _o

[fastrazz89]

You should be able to run a stock carb and stock exhaust with your 70cc kit. It sounds like your jetting is off. Check your sparkplug, see if you are running too rich or too lean.

[enordrum]

Hi all,

Ok, I got a 70cc kit, fitted fine, started fine. Acceleration is good, idles fine. But once I get going i cant maintain a high speed, i get to about 15mph and thats it. It will cough and splutter. I'm using the standard Y12P carbie with a bigger main jet. To say the least I'm getting mad as hell with it. :mad:

Any suggestions?

Cheers

Have you done anything with your torque spring, clutch springs or rollers yet? Install the piston correctly (not backwards)?

[DrDoom]

You should be able to run a stock carb and stock exhaust with your 70cc kit. It sounds like your jetting is off. Check your sparkplug, see if you are running too rich or too lean.
Could be, but I'm having trouble setting the carbie up. Might take it off and strip it down again, see if anythings clogged. I can check the spark plug then too.

[DrDoom]

Have you done anything with your torque spring, clutch springs or rollers yet? Install the piston correctly (not backwards)?
Yeah i installed it correctly, everything else is stock. The 70cc kit was a forced upgrade when the 50cc piston gudgeon pin worked its way loose :(

[DrDoom]

I must have some of the hoses wrong. Anyone got a pic of what hose goes where?

[enordrum]

There's just the fuel hose and the vac line that goes to the fuelcock. I'll take a look at mine later for you.

Airfilter been cleaned? Your belt is good? Mostly it sounds like you have a dirty carb. When I got mine, it idled good but would then die on accelleration, I had a spec of dirt that was getting sucked to the jet and clogging everything up.

[DrDoom]

Cheers, pulled the carbie off some hours ago. I'll give it a clean 2morrow.
I saw on the left side there is that looks like its for a hose attachment. Ill try getiing a pic of it, see if any light can be shared on what its for.

[enordrum]

Cheers, pulled the carbie off some hours ago. I'll give it a clean 2morrow.
I saw on the left side there is that looks like its for a hose attachment. Ill try getiing a pic of it, see if any light can be shared on what its for.

There are actually 3 connection, 1-oil supply (small brass ribbed fitting), 2-fuel supply (large fitting), 3-vac line (where carb mounts to manifold). If you have compressed air, blow out the jets real good while the carb is still wet with cleaner. Have you checked your rollers for flat spots? Checked you clutch shoes?

[DrDoom]

I will give it a good clean tonight and have a look at the rest. It's out of rego now, so I can spend some time on it. Have in mind a full strip down, clean and paint. The plastic is getting old now, might re-enforce it with some fiberglass.

[DrDoom]

Ok carbie cleaned and installed. From 0 to 1/2 throttle great! 1/2 to wot it dies.
Am I right in guessing it is the main jet? I have an 88 installed, is it to big/small? For a 70cc kit?

[enordrum]

Does it just fall on its face as soon as you go wot or does it slow down and die? Air filter clean? Airbox connections good? Look for a crack in the manifold also. This just start or just after a 70cc install? Does it bog? Any smoke and what color? Pull your plug as soon as it dies to get a good read.

[DrDoom]

Slows down and dies, even with the air filter off. I'll give the mainfold a check over. This has only started since i fitted the 70cc kit. Smoke color is grey and plenty of it.

[zumlander]

I would recommend experimenting with different roller weights. I had a similar issue. These zuma's are very finicky, any slight mod and it won't run right, buy a pack of various roller weights and find the one that works.

[enordrum]

Slows down and dies, even with the air filter off. I'll give the mainfold a check over. This has only started since i fitted the 70cc kit. Smoke color is grey and plenty of it.

Do not run it without the airbox on, it will run way lean and cause you to seize! Sounds like you're lean. You probably have an air leak as stated before, check manifold for cracks or dry rot, make sure manifold is bolted down tight, make sure carb is clamped to manifold tight, check airbox connection to the carb and to the airbox and also check that piece for cracks. You also need to upjet your main with the 70cc, if you are using a stock carb start with a 95 on the main with a stock airbox and lower the needle clip (raises the needle) 1 position or maybe even 2. Do check your plug just after it dies also, it will give a hint on whats going on.

A tiny particle making it to the main will also cause it to fall on it's face but you say it's all clean now. Your fuelcock may also be flowing slow but check everything else first.

[DrDoom]

Ok, I think I've fixed the problem. It appears it was running rich, so rich it would flood and stall. I moved the c-clip on the main needle around and now it's on the second from the top. Went for a quick blast around my car park, didn't stall at wot. Not producing as much smoke, before it was belching out. Hope this sounds ok.

[enordrum]

Make sure you do plug chops at 1/8, 1/2 and wot. Weird becasue if you were stalling @ wot...the needle is supposed to only control 1/8-3/4 throttle. Wide open is the main jet function. Was there any oily wetness around the manifold base?

[DrDoom]

None that I could see. i did a plug check before i started working on it, it was soaked in fuel and fuel was coming out of the overflow (wonder why i was going through half a tank so quick). Now the plug is a light brown color. I will give it a ride tomorrow, hope it doesn't lean seize.

[DrDoom]

I would recommend experimenting with different roller weights. I had a similar issue. These zuma's are very finicky, any slight mod and it won't run right, buy a pack of various roller weights and find the one that works.
You know what? I think you're right. What weight are the standard ones? Logically if it can wheel stand from a full stop and i max out at 45Kph, it must be the variator and rollers. Ah well, I need a new exhaust as the baffling has come out in solid chunks and the pipe from the exhaust outlet has a big kink in it. Money money money.

[enordrum]

Kink in the exhaust would be a good place to start, that will affect your top end greatly. Are you running stock exhaust? Mine had a clogged screen on the metal cone screen that I cleaned out and it helped a bit. 45kph is slow, definitely something wrong there. Keep us posted.

[DrDoom]

Ok, update. Have new clutch, clutch bell, rollers, variator. New carby on the way and new carbon fiber reed. Just saving for a new exhaust, prolly a Giannelli Next. I can't find a new front end for a brake upgrade, but it's a work in progress. Should go like a rocket after all the mods. Plus I'm having a ball working on it. :D

[DrDoom]

Engine pulled apart and tightened head bolts, ordered new exhaust. Still waiting for carby and carbon fiber reeds(looks like they got lost in the post) Cleaning everything.