BP9HS spark plug issue

[yama916]

so I experienced my first spark plug fouling on my zuma the other day. sure enought it died and DID not restart. had to push it home 30min... so about spark plug fouling...

what causes it and can it be fixed?

i cleaned the fouled plug with raw gas, some steel wire scrubbing but it still ran bad after all of that. when I installed a used clean plug it ran great.

stock zuma came with BPR7HS, some one on the forum said P stand for longer tip. why is that a bad thing? (some one said it wasnt as good)

70cc airsal kit came with BR9HS, 9 for a different heat range, but why do they use a shorter plug? When I used a BPR7HS on the 70cc kit because I had nothing else.. it did not hit the piston and it ran great.

so can some one explain? thanks
yohei

[XPS1210]

basically it usually means your rich on the top end...

The stock cylinder is low compression and needs the spark plug further in the cylinder to allow it to ignite the fuel easier... the t6 is considered a medium to high compression cylinder and doesn't need the extended plug for ignition...

the stock cylinder runs fune off of a 7 heat plug... however the aluminum can get to hot easily and melt due to the hotter plug...

I ran my T6 with the stock plug for several hundred miles... and I had oil burns on the inside of the piston (near where the pin is inserted) this is caused by the piston becoming to hot... More than likely from either a lean condition or from the plug being to hot... and I was running the 7 heat plug at the time...

Back to the way to correct the dead plug issues... once a plug goes bad... throw it away, the thing gets wet and it's garbage... You need to work on what causes it to be rich... if it's your WOT, then it's you jetting... if it's while running at 1/2 throttle then it's your needle that needs adjustment, and if it happens at idle you need to adjust the fuel air mixture and idle screw to accomodate the correct idle.

Hope this helps.

[str8dum]

This the the ngk guide to plug reading
http://www.ngksparkplugs.com/techinfo/spark_plugs/partnumberkey.pdf

it wont hit the piston because its still an H series plug. LC kits need an E series plug which is 6.3mm longer.

Not sure what they mean by projected tip with the P letter but with a AC 70cc kit, u need to run br9hs. Plugs are $2 each. Why even bother trying to clean them? If you think its bad, just put a new one in. You can buy them from any autoparts store. So stock up.

[yama916]

great info guys, and really helps! thanks!

i do stock lots of plugs for my car, and replace that often, but didnt expect to happen so soon on the zuma. it was running very rich, and after my recent fouled plug incident and some more tuning, my plug was brown as it should be. and it accelerate and runs pretty good even at 1/2 throttle so i dont think i will foul another plug so soon.

I will go stock up.. but if it went bad, and i happened not to have any spare, is there are sure way to clean it ? soaking it in gas, scrubbing with steel wire and compressed air did nothing... how does it go bad what is making it work so badly? as after i cleaned the bad plug my zuma RAN, just really rough at almost didnt run at WOT.

[yama916]

i ordered a set of BR9HS-10, thats all they had, 10 stands for 1mm or .04'' gap i guess. what is the right gap for the 70cc airsal kits?

[mikhail masevich]

im runing a b8hs ngk is this normal? I have a 70 cc kit polini clutch and premixing 40:1 redline using 91 octane gas? How does the heat work the higher the number the hotter the plug runs? I have a polini for race exhaust any ideas what is a good set up im still learning.

[pinkymingeo]

With NGK the higher the number, the colder the plug. Stock uses a 7, iron cylinders 8, the T6 a 9. I have a lot of compression and not much squish, so I run a 10. I've never fouled a plug, but always have a spare under the seat. You never know, and plugs only cost $2.

[mikhail masevich]

Pinky After i changed the polini cluch. Sometimes when the bike is not running i rool it around not started and it makes a scratching noise it sounds like the cluch is rubing on the clutch bell. And sometimes it doesent rub. I think i should just put the stock clutch back there is no diference o_o . Can i get a 9 ngk plug at the dealer what is the spark plug # i have to get

[mikhail masevich]

I went around looking for a bpr9hs plug nobody said they carry that plug maybe i messed up on the numbers. checked yamaha ,auto zone and all the stores. What do i tell them what sparkplug # i need. Because after running my zuma for 20 minutes i pulled the plug out and it seemed to be kinda white not brown there is a ngk now in it ngk 8 heat i need a 9 heat fast.

[XPS1210]

They don't make the stock number plug in a 9...

BR9HS is the replacement plug as NKG stopped making these plugs a few years ago... Basically one is longer then the other (the new one is shorter) and work the same due to the compression on a 70cc kit being higher then stock....

[pinkymingeo]

There are only a couple of auto parts places around here, and they stink. I used to get plugs at the discount marine supplies place. A lot of outboards use the NGK 7-9 series. If the day comes that you need a 10, gotta go internet. Nobody stocks them. If you want to play around, **some online places*** have about everything. The shipping will kill you, though, so I order a dozen at a time.

[XPS1210]

erich at provo sells the ones I listed...

$3 each I think... and he ships usps so it's not that bad...

look at www.provoscooter.com for them...

[mikhail masevich]

Put a BR9HS plug today it ran good then after like 10 min riding it it will go slower and slower. And it seems to be white. Give me some thaughts guys im having trouble starting the engine when its cold. It fires first kick then dies if you give it a little bit of throtle.Then with throtle all the way closed you have to kick about 20 times before it starts idling. Im running a 17.5mm carb from a derbi. I think i may be running to rich because im premixing and still think my injector is working.And one more thing i put a polini clutch it was ok but when i put my stock clutch back in when i go and stop the clutch still tries to be grabing at idle. :angry:

[XPS1210]

sound like your LEAN... turn the idle screw out... (left) then if it's still lean... you can drop the needle one.. and so on till it's no longer lean...

[pinkymingeo]

Usually when you have trouble starting the pilot is too small. The carb is definitely lean.

[mikhail masevich]

Ill try to make it richer. I heard my friend say when premixing there is a line that runs to the crankshaft to lube the bearing is this true? Because im planing to take my injector off and scared to fry my crankshaft and bearing.

[str8dum]

there is no such line.

the crank turns a gear on the pump which takes oil from the oil tank and into the cylinder

[florida derbi rocket]

Mick..If you Pre-Mix...You cant go Wrong..It's kinda like Eliminating the Middle Guy..Your Cylinder Wont fry..The correct amount of oil will always be in the Combustion Mixture....Dis-able that oil Tank/Pump..Its The 2-Stroke Insurance...It's also One more thing to go wrong.....John. ;)