1975 Montesa Cota 247 - Starts Superbly Now But Struggling With High Revs.

[handmadematt]

I don't think it was the spark plug, same thing happening with a different one.

You will be able to read the size on the main jet as it is easy enough to read. The Pilot will need to be unscrewed with a small flat blade screwdriver and also where the needle clip is will give us info on the set up, likewise the slide may also be marked numbers from 1.5 to 3

Thanks Tony. This morning I've not opened the carb fully yet so can only report back that the throttle slide is number 3.0 and the needle clip was on the second from the top groove. Again, it's the Mikuni carb.

I moved the clip to the bottom groove and the problem became much worse, much to rich, the clip is now on the top groove and it's improved a bit but it's hard to tell.

its not a moto cross bike nor a fast road bike its designed for the torque to be used more than hi revs ,its not very often you would get into a situation where you need to be flat out other than up a steep hill ,unless your trying to keep up with enduro bikes its not ment for that , you really could do with someone that has more experience with this type of bike to have a ride it could just be too rich top end or your expecting too much from the old girl

Thanks for the contribution but I'm confident that it wasn't like this before, this morning I tested again after moving the needle clip and this is what happend:

Having warmed it up I held the throttle wide open and it reached the limit where it "choked" it felt held back like it's being limited of air, or fed to much fuel, if I held it in this uncomfortable position it cleared a couple of times and reved right up nicely beyond this ceiling, so something is definitely funny.

Maybe it's running to rich for some reason? (It's not smoking.)

A funny thing that is worth mentioning is I left the fuel on last night by mistake and it was leaking from the carb, (I think the gasket's a bit rubbish but it might also have been coming out the overflow pipe because there was petrol ice crystals on the end of it, it was a chilly night and the evaporation can make it freeze like this.)

Maybe my float hight is to high?

All that opening and closing the carb might have changed it, I was carful but maybe I bent the brass arms slightly by mistake.

If I lower the float hight will that have the effect of making the mixture weaker?

Is there a recommended float hight for the Mikuni carb with the Cota 247?

Thanks again.

[jfc]

I have scanned the manual to a PDF let me know an email address and I will forward it to you.

[handmadematt]

The problem seems to have cured itself after a good day of riding. Maybe she just needed a good thrashing?!

[mboon]

JFC can you send me the manual please

Edited February 2, 2018 by mboon