We have a 94 mc28 with JHA pipes and HRC 030 card otherwise it's stock.(motor's fresh)

Running a 142/145 mains, stock needle, 40 pilot with stock powerjets and it's pretty well perfect colour with no issues on acceleration at all. Starts fine as well.

Heres the wierd part: Its perfect running at 0-1/2 throttle, but as soon as you open wide open it goes onto one cylinder, doesnt stutter it basically runs to one cylinder (or goes flat on power. You role off and it picks it back up, happens anygear, anytime).

The front cylinder is black (plug) but still sparks under 1/2 throttle. I have changed the plugs and it's the same.Havent replaced the plug cap yet.

So basically its running perfect on the upper cylinder and the lower one's fouling at wide open throttle.

Powervalves and oil pump are set perfect.

Any ideas?

Gonna swap the plug cap tomorrow and possibly switch the coils to check them.

Anything else to look for? Pickups? Possible stuck ring?

Thanks in advance.

Yeah, the coils can break down at high RPM, so once you've checked the cap, (or replaced it to be sure, they're cheap enough) then try swapping the coils to see if the fault swaps to the upper cylinder.

Another thing whilst you're there, is to check the connectors for the coils. It doesn't take much for the to get a bit loose and start to go black and pitted. This builds up resistance and causes bad running. Give 'em a good clean.
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

ok,new caps,new plugs again,still does it.I swapped coils around and it still did it.
i puller lower cylinder off to check for stuck ring but its ok,the powervalves are sticking though,i guess when it was re-nikisaled they didnt clean the edges and the powervalves touch.i cleaned them up and now move freely i will try that out next.

the float levels at 13.7 sound alright?

i tried the stock card as well as the 030 and it reacts the same.

will any of the air T's cause this?iam focusing on the front cyl only as the rear is running perfect.I would think the floats would leak down even at 0-1/2 throttle so i havent played with them.

I dont have a manual for specs on this so any helps aprreciated.

i'll post pics of plugs after work.

ok i have covered pretty much everything,the front cylinder i found out was siezed before and was renikisaled and a piston fitted and a new crank,the bike ran perfect before that was all done,as well it was de-restricted by them to.

now it fouls the lower plug on high revs.

is it possible the cylinder isnt right?causing blow by at high reves?
or could they have messed up the wire splice.de-restrict?
could the right crank seal be bad and sucking tranny fluid causing this?

its only lower cylinder.

normally i have this stuff fixed by now but iam searching for things that another place did.also dont have a shop manual either for specs.

thanks

The only specs you'll find are on this site to be honest. There are no manuals available in English.

How's the jetting? I'm beginning to think it's not electrical problems...
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

I think the jetting is nearly spot on, the top cyl anyhow. JHA pipes, 030 card, stock airbox, de-restricted. Pulls really hard with no hiccups, but as soon as ya give full throttle it goes to 1 cyl. Role off and it picks up straight away.

145/148 mains
40 pilots
13/4 air screws
stock power jets
stock needles
13.6 float height

The top plug is light tan with the ring 1/2 way up the porcelin, the ground electrodes 3/4 almost white.

the lower one fires fine until i open the throttle wide open then it goes black or onto 1 cylinder,it doesnt foul it as i roll outa the throttle and it picks it up again.

the lower cyl was redone by someone else as well as the derestict mod and the 030 card etc..it ran fine before he had it fixed fron the sieze there.

its baffled me alot as normally i can fix these in no time but this is a odd problem.

i wnet as faar as to lean it out bigtime,138 mains and the top plug was pure white(luckily no sieze or deto)the lower one was excatly the same.soaking wet and pulled exacty the same.do you know if any of the mc21 electrical is the same?or is it possible its suckin trans fluid from the right seal?


anyway thanks for the help.

Hang on Jester, in post one you said 142 / 145 jets. now you say 145 / 148!

If all other things are set up correctly, it does sound like you are rich on the front cylinder.

Do you have a jet kit?
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball