Keihin Carb set up?

Yes, I was surprised about the washer and O ring but I checked and they are selling it for a PWK 38 (and others) so who knows?

I did spend some time yesterday and accurately marked 16mm on the carb and lined up the float at 60 degrees and it seems to start, idle and run much better. Note: I refitted the original Keihin slide at the same time and it is obviously much better quality than the (must be a Chinese copy) new one.

Reeds wise, I removed them and to me they looked perfect. Good clean edges and no obvious wear... having said that, this is the first time I have ever seen a "reed"!

I have just found a suitable O ring and fitted it. I have to say it has helped steady the tickover and I left it at idle for a good 10 mins with no issue so seems to help.

Also, I have had a ride on a bit of rough ground (out back) and it feels good. The exhaust has a nice "crackle" (although that may be bad!) It pulls well from low revs and has a real kick when opened up a bit. Good solid idle and starts easy hot or cold.

Subject to a road test, I think it is pretty good and certainly nice to ride.


PS.. Is it me or is this bike incredibly well balanced/stable at low speed? I have a trials bike and it feels as good as that... very impressed with its balance...
 
as this is most likely in contact with fuel I would suggest using a nitrile or viton o-ring. I think the normal rubber ones may end up disintegrating (not sure where the disintegrated portions would go)
 
178/40 N3EH 2nd groove from top.

Final update..

Thanks to all for the useful advice and guidance. I am now happy with the N3EH on the 2nd groove from the top and 178/40 jets.

The NEDJ was good but it ran quite rich with lots of spooge and smoke.

I now have a clean steady idle, nice linear throttle response, comfortable low speed control and a nice pick up when I get enthusiastic. The smoke has reduced a lot and the black stuff from the exhaust has reduced dramatically. Starts first or second kick hot or cold. (needs choke when cold)
It has a nice crackle and overall feels like a lovely controllable bike.

It does rev higher than I would like on a cold start with choke.. not sure if that is normal?

Anyway, I will be glad to get it out on the cold and wet Welsh mountains and see if it performs as well as I think it will.

Thanks again...

John
 
Excessively high idle with choke?

Hi all, the bike (2007 EC250) is running very well now with an N3EH on the 2nd clip and 178/42 jets. Starts 1st kick hot or cold and no excessive smoke or spooge. Idles nicely when warm.

It does, however, idle really high from a cold start and then after about 30 seconds it drops down to a normal slow idle. The throttle cable is free and does not appear to stick and the choke unit has been removed and appears in good condition.

A quick google shows that this is common on some other 2T bikes but the conclusion seems to be that it is normal?


Any thoughts on why the choke idle is excessive and why it slows down after a short while?

ps.. it did not do this with the original carb set up.
 
It looks like I have solved the problem...

On closer inspection I noticed that the air box at the back of the carb was not fitting properly on the right hand side of the carb intake.. it was difficult to see but the carb was not snug inside the plastic/rubber air box and may have been leaking air.

It was very difficult to remedy and I had to heat the air box and force it into position by releasing the front intake rubber and moving the carb rearwards, tightening the large hose clamp, then moving the carb forward onto the rubber intake manifold and retightening that..

The air box appears to be deformed and I shall have to remove the seat and tank tomorrow and try heating it up again to get it into a better shape to fit its intended purpose.

The good news is it has solved the high idle with choke issue!

Different carb but useful info.. https://www.youtube.com/watch?v=Uid8L4yMvfc

PS. The next day it was 12 degrees warmer... up from minus 2.
This had a significant affect on choke idle speed which was reduced.. Maybe air density plays a part?

Anyway all good now...
 
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