Float height doesn't make sense??

[BlackScreener]

I have a similar problem with EC 300 2001. My settings:
- new S3 cylinder 2013 or 2014
- new 2014 cylinder head
- new Vesrah crank
- all new bearings in the engine
- new pipe from ec 06 or 07 without catalyst
- cdi from 2001
- new ngk br8es plug
- new hiflofiltro air filter from cr 250 00-01
- stock muffler

Carb is PWK AS1:
- N3EG needle, 3 clip from top
- 42 pilot jet
- 178 main
- 7 slide
- new boyesen reeds
I run it without reed spacer.

Before rebuild, engine lacks with bottom end power. I thought it was problem with 250 97 cylinder in my engine but with new 300 cylinder still bottom was weak. I found that it was caused by the exhaust valve. The valve opened too quickly. 1mm shim made the deal, now I have got bottom end power. However, with 178 main engine feels rich and don't rev. With 176 revs seems well but only if engine is well heated. 174 main seems flat at top and it is hard to say that max rev is ok. Only 176 jet works good, but power wheelie at 4th gear is almost impossible with 13-48 gearing.

Piston at BDC is placed with top of the exhaust port. Squish is 1,60-1,70 mm.
16 or 18 mm float height doesn't make any difference in my case. It revs to 9800-9700 rpm with 176 main, but it could only be on stand.

Can too much shims in power valve be the reason of tamed engine?

[Davehuge]

Hi Blackscreener

You mention trying different main jets and how the bike feels... have you tried doing a plug chop at Wide Open Throttle?

I thought my bike felt rich at WOT but in fact I was wrong, doing a plug chop showed the plug was grey and obviously lean.

Just waiting for my 180 jet to arrive so I can try it.

Have you seen the power valve actually rotating as RPM increases? I removed the LEFT side power valve cover and marked the end of the shaft, it can easily be seen rotating.

Good luck, Dave.

[BlackScreener]

Hi Davehuge.
Thanks for response. My spring valve seems to be worn out. With stock 0,7 mm shims bike lost bottom end power. I add 1 mm shim and it help nicely to bottom end power, however I struggle to get top end rev and power. I did a plug chop witch 176 main and plug seems to be white/grey. Maybe little lean but not so bad. Still I would prefer 178 in this condition i.e. 80 meters above sea level, 15-30 deg C, 40-50% humidity. Today I pulled out 0,5mm shim and engine revs better with 178 main but feels flat, seems that exhaust valve spring causes problem with over rev. I think 18 mm float height is too much (Not enough fuel in the carb), I will back to 16mm. Yes, I checked power valve, it works good.

[Davehuge]

Hi, you said that after plug chop it looks a white/grey, sounds lean to me. I would like to see a brown tan/chocolate brown.

If it's lean maybe that is another reason why it's losing top end power?

That's the problem I have at the moment.

Good luck! Dave.

[BlackScreener]

Yeah, you can be right. Too lean isn't good for top end power. I will stick with 178 main.
What needle have you got? Also check your float height.

[Davehuge]

My needle is the standard N1EF. To be honest from CLOSED to 3/4 throttle I've got it running really nice, it's just WOT I have a problem with, so I hope the bigger 180 main jet will fix that.

I checked my float height, it was about 20mm. I set it to the recommended 16mm but I kept getting the odd drip from the overflow. When I remove the carb to fit the bigger main jet I will try setting the float to 18mm.

Fingers crossed!

[BlackScreener]

Mayby 20 mm float height causes lean conditions. Try 17 or 18 mm. N1EF also is pain in the ass. If bigger main jet and other float height don't help try another needle, eg. n3eg with 40-42 pilot and 176-178 main.

[Davehuge]

Fitted the bigger 180 main jet but I still have the same problem...runs great from CLOSED to 3/4 throttle but won't pull WOT - Wide Open Throttle.

Did another WOT plug chop with the 180 jet but the plug still looks grey - lean.

I've now ordered a 185 main jet, but if I still get the same results with then I won't be going any bigger. I'll then be looking for an air leak somewhere, possibly left side crank seal.

Cheers, Dave.

[Jakobi]

Not something electrical? I thought the older CDI units were a bit soft up top... (read it - no personal experience). Coil breaking down at higher revs? Spark plug? You'd expect some unburnt fuel though.

How is the ignition timing at the stator?

[Davehuge]

Hi Jakobi

I don't think it's electrical, if I feather off from WOT, gently close the throttle a little then it pulls and revs really well.

Also tried a brand new spark plug, but just the same.

185 main jet should arrive in the post tomorrow, so will try that and see what happens...can't see any point in going bigger...can you?

Thanks, Dave.