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Overheating problem?


netley
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It does take a lot of time and patience to get them running crisp, this video is maybe three years old and I think it would have had a Keihin on it. I have run with a dellorto but I would have to say the keihin/oko is the easiest to get running crisply.

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Does run but not very nice still a bit lean and still not crisp. The engine does rev a bit longer after a throttle burst then it should.

 

I believe the carb is worn out typical slide, needle and jet.

The engine can also run much slower in idle mode, Sherpas love to rev slow when ideling I strongly think there is still another issue

 

Edited by pschrauber
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10 minutes ago, pschrauber said:

Does run but not very nice still a bit lean and still not crisp. The engine does rev a bit longer after a throttle burst then it should.

 

I believe the carb is worn out typical slide, needle and jet.

The engine can also run much slower in idle mode, Sherpas love to rev slow when ideling I strongly think there is still another issue

 

The carb is brand new, supplied by    https://www.inmotiontrials.com

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Mmmh then there is something different the issue.

The engine sounds as it don't want to accelerate right and when it finally archieved some rev and you close throttle the motor want's to run away but doesn't have the power ... so finally decides to slow down.

- Timing of the ignition?
- How does the plug color picture look like?

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The slow return to idle speed is a classic symptom of an air leak - possibly from crank seals, the intake stub to barrel gasket, carb connector or centre case gasket. The 64mm stroke engines (eg. 350, 360 and 370cc but not 325cc) have a tendency to leak around the centre gasket as there is very little material between the crankcase and a couple of the stud holes. 

If it's very slow to drop back to idle - and especially if it makes that " imm bim bim bim" sound while doing so - then I'd be doing a pressure test. It's either very lean at idle or it's leaking air. And of course the other common symptom of an air leak is a cooked or seized piston....

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I run a VM26 on my 350 M199; it runs perfectly on this jetting so it might be a good place to start:

120 main (summer) 130 in winter

N8 needle jet, 5DP39 needle (better from 1/4 to 1/2 than 5F21)

clip in middle groove

60 pilot

Screw 2 turns out

2.0 slide

0.5 air bleed

Bear in mind summers here are around 25 - 35C, winters around 10 - 15C

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1 hour ago, sherpa325 said:

Netleys bike sounds like it needs a larger pilot to me,however its  very difficult to sort out just watching a video

That's what it sounds like to me, too. But if it turns out to already have a 50 or 60 in it I'd be having a good look for an air leak before putting an even bigger jet in. Probably sounds worse than it really is because the idle speed is set high.

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Thanks for sharing your collective wisdom, much appreciated.

The crank seals were changed recently during re-build and hopefully cooking the piston didn't do any harm. I will check for possible air leaks around the carb and see what jet it's fitted with.

New OKO carb will hopefully arrive today.

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7 hours ago, oldjohn said:

I run a VM26 on my 350 M199; it runs perfectly on this jetting so it might be a good place to start:

120 main (summer) 130 in winter

N8 needle jet, 5DP39 needle (better from 1/4 to 1/2 than 5F21)

clip in middle groove

60 pilot

Screw 2 turns out

2.0 slide

0.5 air bleed

Bear in mind summers here are around 25 - 35C, winters around 10 - 15C

Well I can't read what stamped on the pilot jet so I have no idea !

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