Float height doesn't make sense??

Davehuge

Davehuge

Member
Hi all

Recently bought a 2004 EC300.

I've been trying to get the carburetor set up, I've made big improvements but it's not 100% right yet, I need some help/advice.

Carb is as follows...

38mm Keihin PWK38
Main jet 175
Pilot jet 40
Needle top notch (leanest)
Air Screw 2.5 Turns out

As you can see I've got it set pretty lean compared to most people's settings.

From Closed to 3/4 Throttle it's working really well. But it won't pull wide open throttle, feels rich. If I close throttle a bit I can coax it to pull the full open throttle.

I suspect the main jet is too big/rich but at 175 it's already smaller than a lot of people are running.

Another suspicion I have is that the float height too high. I've read some of the threads and I keep seeing the figure of 16mm quoted as the correct float height, but that just doesn't make sense to my carb. I measured it and it's already at 21mm. I'm sure if I set it to 16mm it would be running even richer and or overflow.

Is it possible that I have a different version PWK38? Bearing in mind that it's a 2004 model?

Any help/advice greatly appreciated.

All the best, Dave.
 
Forgot to say...

Air filter is clean and oiled.

I'm running at about altitude 300m (1000 Feet), temperature around 25'C (77'F).

Thanks, Dave.
 
Check your silencer packing. I had a clogged silencer and my bike (2011 300) exhibited similar tendencies. I tested the Keihin as well as a Lectron, no difference in symptoms. Swapped out the silencer and problem solved. It's worth a look to see if the silencer is plugged or not.
 
Results from plug chop...

Reset the float height to the recommended 16mm and went for a ride today.

Bike's running great CLOSED to 3/4 throttle but still won't pull Wide Open Throttle.

I felt it was running rich and decided to do a plug chop. To my surprise it looks like it's lean. Currently on a 175 main jet. Definitely looks grey.

I've just ordered a 180 Main jet, see how that goes.

Yours comments...?

qrx36d.jpg
 
Davehuge said:
Hi all

Recently bought a 2004 EC300.

I've been trying to get the carburetor set up, I've made big improvements but it's not 100% right yet, I need some help/advice.

Carb is as follows...

38mm Keihin PWK38
Main jet 175
Pilot jet 40
Needle top notch (leanest)
Air Screw 2.5 Turns out

As you can see I've got it set pretty lean compared to most people's settings.

From Closed to 3/4 Throttle it's working really well. But it won't pull wide open throttle, feels rich. If I close throttle a bit I can coax it to pull the full open throttle.

I suspect the main jet is too big/rich but at 175 it's already smaller than a lot of people are running.

Another suspicion I have is that the float height too high. I've read some of the threads and I keep seeing the figure of 16mm quoted as the correct float height, but that just doesn't make sense to my carb. I measured it and it's already at 21mm. I'm sure if I set it to 16mm it would be running even richer and or overflow.

Is it possible that I have a different version PWK38? Bearing in mind that it's a 2004 model?

Any help/advice greatly appreciated.

All the best, Dave.
Click to expand...

This is a good thread on float height from another site.

http://www.allthingsmoto.com/forums/f-31/float-height-doing-right-way-65541/
 
By the way... after doing the wide open throttle plug chop and seeing the grey plug (as in the photo) I rode home then inspected the plug again. It was a nice chocolate brown/tan colour.

So it would seem I have good carburation at other throttle positions, just wide open throttle is lean. Hopefully the 180 jet I've ordered will do the trick.

All the best , Dave.
 
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?
 
Last edited:
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.
 
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.
 
Last edited:
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.
 
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.
 
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!
 
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.
 
Fitted the bigger 180 main jet...

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.
 
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?
 
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.
 
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