Overheating problem?

[netley]

Getting a magnifying phone app was easier than trying to track down my dad

Went on a practice session last night and the bike ran well but still not quite right. Some footage here.

I spoke to Dave Renham at Bultaco uk this morning who said the pilot jet reccomended for the Mikuni I bought from him was 30 so I've got conflicting info.

I can get a 45 locally today just to see what difference it makes?

What are your thoughts?

[carl ekblom]

It might be as simple as closing air screw and make adjustments to needle position. Basic setting for air screw would be 0.5-2 turns out.

 

 

 

 

[oldjohn]

2 hours ago, netley said:

...I spoke to Dave Renham at Bultaco uk this morning who said the pilot jet reccomended for the Mikuni I bought from him was 30 so I've got conflicting info.

I can get a 45 locally today just to see what difference it makes?

What are your thoughts?

Maybe there are differences between your engine/carb and mine, but I'm sure that if I tried to run a 30 pilot in my bike it'd take about a week to warm up enough that it didn't hesitate on opening the throttle. I'd try the 45.

[sherpa325]

I would be interested to know how many turns your air screw is out, every time I hear your bike it sounds like it needs to be wound in 1/2 to 3/4 of a turn

 

[carl ekblom]

This is what I use mikuni vm26: Needle 5C23, throttle 2,  main jet 140, idle jet  30, needle jet O3, needle first groove from top (French Trial Classics jetting). Air screw is 1 turn out

Edited April 27, 2017 by carl ekblom

[netley]

Couldn't get the pilot jet in the end. I'll have another go tomorrow and reset the air screw......again

[woody]

60 for a pilot jet in a Mikuni is huge...  On Yams, Bultacos or Ossas I've never used bigger than 35.

Listening to a bike on a PC completely distorts the sound and makes them sound worse than they are, but yours sounds as though it needs the exhaust repacking, it sounds noisy. If it's blown all the packing out of the middle box, or it's gummed up, and the same with the bottom half of the rear box, it will definitely make it run rough off idle

[bondy]

As Woody says the exhaust needs repacking I always get mine done on a new rebuild also if your engine as been rebuilt you will need to run the new piston in you will find the carburettor will need a few tune ups until the Engines run in.

[netley]

10 hours ago, bondy said:

As Woody says the exhaust needs repacking I always get mine done on a new rebuild also if your engine as been rebuilt you will need to run the new piston in you will find the carburettor will need a few tune ups until the Engines run in.

Thanks, I'm just running it gently with brief spells with wider throttle openings, anything else?

Also so how does one re-pack the exhaust?

Cheers.

Neil

[bondy]

You have to cut open the middle section off the down tube there's 2. Ways of doing it first you can cut the rear open where the exhaust gets bolted the Engine second is you can cut open near the bottom where it joins  to the rear some 1 will have photos are I think there's a topic on it search for it. You need to clean all. The old crap out there's a perforated tube inside that slots into 2 collars take it out and clean then put back in. You need exhaust packing only cheap  there's loose and pad type I use pad type cut into strips and wrap round the complete tube not to tight but not to lose stick the plate back on you cut open and weld up done am sure some have different methods.

Edited April 29, 2017 by bondy