LCGB Forums

Hi Guys
I'm losing my sanity with engine misfire/splutter in 4th gear after 1/3 throttle. It revs ok in 1st, 2nd & 3rd gear but in 4th it wont run correctly. Engine is tuned 225cc TS1, these are things I've tried below:-
Changed Plug
Changed plug Cap
Changed HT lead
Tried 3 CDI units
Cleaned out carb, jets etc
Flushed out fuel tank
Petrol flow exceeding 1 pint in 60 seconds
Taken green wire out of CDI to eliminate any failure in the wiring
Changed reed petals
Replace old Mikuni carb with Mikuni new carb. jetting the same as one taken off
Old stator replaced with new BGM stator with pick up height packed and checked and strobed
Old flywheel magnets loose, so replaced with new flywheel. Re-timed and strobed.
Any help is most appreciated

Is it a misfire or poor engine response at speed? Are you running an air filter?

Mark

Solid Air wrote:Is it a misfire or poor engine response at speed? Are you running an air filter?

Mark

Open bell mouth, no use of filter. It seems to accelerate in 1st to 3rd gear but in 4th after 1/3 throttle it misfires/splutters /engine holds back and won't clear. I assume if it was jetting it would splutter under acceleration

I'm no expert and there's some really knowledgeable people on here Celt but as it looks like you've already covered a lot of things, I'm wondering did the fault develop on its own or had you changed something or maybe rebuilt the engine?

Solid Air wrote:I'm no expert and there's some really knowledgeable people on here Celt but as it looks like you've already covered a lot of things, I'm wondering did the fault develop on its own or had you changed something or maybe rebuilt the engine?

The fault has developed on it's own, I tried the above to rectify the fault. Now I'm at a total loss

Try putting the choke on in 4th when it starts playing up. worked for me years ago on one of my old bikes. Indication of lack of fuel combined with resistance. Fingers crossed.

You've covered about everything I can think off, except..................breather hole in fuel cap.......must be worth a clean.

good luck

I had the same symptoms recently and i could only put it down to fuel starvation but all the usual checks were ok.

Mine turned out to be a carb problem. I'm not saying yours is, but when you say you changed the carb, did you change it completely or did you leave the float bowl for example? (Forgive my ignorance of mikuni carbs).

I once had the same kind of problem on a ts. I did all the things you've changed rode half the season really struggling with the scoot. I got back from brid the last rally and pulled the bike apart. Normally I would take my pipe off in one piece. But as it wasn't going back on I split the pipe down into pieces. Removing the rear muffler section only to find a blockage in the pipe. It was a Taffy mk4. Like I say up until that point I'd been removing the pipe in one piece. After phoning a couple of the lads to tell them ov my joy of finding the problem. I was told if you ever took the bike to AF one of the 1st things ray used to do was rod the pipe even thinking about it it seemed electrical the problem. I'm surprised the bike ran , it never holed the piston as the heat build up must have been immense.
Anyway something for you to check. Good luck.

St George wrote:Try putting the choke on in 4th when it starts playing up. worked for me years ago on one of my old bikes. Indication of lack of fuel combined with resistance. Fingers crossed.

Will give it a go

dickie wrote:I had the same symptoms recently and i could only put it down to fuel starvation but all the usual checks were ok.

Mine turned out to be a carb problem. I'm not saying yours is, but when you say you changed the carb, did you change it completely or did you leave the float bowl for example? (Forgive my ignorance of mikuni carbs).

Changed carb entirely to a brand new one

Dazts1 wrote:I once had the same kind of problem on a ts. I did all the things you've changed rode half the season really struggling with the scoot. I got back from brid the last rally and pulled the bike apart. Normally I would take my pipe off in one piece. But as it wasn't going back on I split the pipe down into pieces. Removing the rear muffler section only to find a blockage in the pipe. It was a Taffy mk4. Like I say up until that point I'd been removing the pipe in one piece. After phoning a couple of the lads to tell them ov my joy of finding the problem. I was told if you ever took the bike to AF one of the 1st things ray used to do was rod the pipe even thinking about it it seemed electrical the problem. I'm surprised the bike ran , it never holed the piston as the heat build up must have been immense.
Anyway something for you to check. Good luck.

I will have a check of the exhaust. I have a new spare end can, no harm in changing it

+1 on the exhaust being potentially blocked. A mate (also on here) had similar issues recently and discovered a piece of inner skin of exhaust rattling around in the expansion chamber which he reckoned was intermittently blocking the stinger internally. He described it as like it was four stroking badly and had put it down to jetting until he took the exhaust off and heard it rattling around

Hi
Air leak under load,putting choke on as st George suggests might help diagnose.also plug chop under load in fourth
Grandpa

Any updates ?

agreed, getting curious.

CARMON its being 18-days now without an update.............
you haven't told us about the Mikuni's jets?

Hope he ain't fell off ?

Sorry guys, I haven't been on the forums for a while. Also sorry to say there are no updates busy with work and too bloody cold in the garage. I will be trying the following when I have chance:-
1. Putting the choke on when it splutters
2. Testing it without the panel on
3. Take exhaust off and check for blockages/obstructions
4. Check all earth points

If all these fail, I will get the gun out

Dazts1 thanks for your advice as I think it's was a coked up exhaust. Took the exhaust off in pieces as you advised. Found cunks of carbon in joining sections. I rodded the exhaust as best I could. Then poured caustic soda, rinsed out, rodded again. Blew out with air line, re-fitted exhaust. Had a ride today and what a difference it made