Continuing problems with my Penton

[dsklcsw]

Hi Everyone,
I have another problem with my 250 Hare Scrambler.  Now that I have a new PVL and the bike will start and run, but it won't idle.  Whoever owned this bike before me replaced the Bing with a 34 mikuni.  The bike runs well above idle, but will die below 1/8 throttle.  I have changed the pilot jet which started with a 30 and is now at 20.  I tried a 17.5 but the bike did not start at all.  With the 20 and above, the idle adjustment screw (works the slide) is all the way in and does nothing.  The air screw does nothing until about 3-4 turns out, then the idle will increase but not much.  The bike is fitted with a 3.0 slide and a leaner than standard needle.  I have not gotten into the needle jet, but that shouldn't affect the idling anyway.  So I am totally baffled.  The plug indicates that it is running a bit rich, and often there is black drool coming out of the exhaust and drips on the engine.  The other jets in the bike are as follows:  200 Main, 2.0 air jet.  Help!  
Thanks...Dwayne

 

[Rocket]

Dwayne
Will the bike idle when you first start it with the choke on?  Sounds like you are going the wrong direction with the pilot jet.  A 20 is pretty lean.  Have you removed the pilot jet and blown carb cleaner through all the passages?  Have you physically looked when you adjust the idle screw that the slide is moving up?  Air screww should end up about 1 1/2 turns out.
Rocket

 

[firstturn]

I agree with Rocket(Rod) on the jet being too lean.  You said you put a PVL on the bike.  Did it Idle before or is this the first time YOU have had the bike running at all?  Just trying to clear things up a little.  Also cleaning your carburetor is sooo critical -  I have helped people get their bikes to run fine after they have told the carbs were clean.  Ok I'll go back to tring to get my 8 Webber carbs in sync.

Ron Carbaugh

[Blue_Dog]

X Cuse ME ROn:

Can you tell us all what year they ran 8 Web's on one PENTON?

HeHe
B-D

 

[OUCWBOY]

Hey B D, I can tell you when that was, it was when Ron the Magic man, made this one manifold and hooked them all up to a berkshire and it would run about a hundread and fity or so! Left all them others in the dust. Hardest part was getting em all in sync. had 8 throtle cables too!

Donny Smith

[firstturn]

OK - It's obvious I'm stumbled into some people that actually know what webbers are - once again the Penton forum is read by the best and smartest people.  Yes Donny the speed was correct in Klos, but those cables were a problem.  And Blue Dog We know your a old racer from Texas so I didn't expect to fool you.  Now if I can just get this computer in my Berkshire to run for more than an hour on the 9 volt battery the EFI should make it scream as long as there is no one checking th CC's.  A very Humble firstturn.

Ron Carbaugh

[Rocket]

Are those down-draft Webber's or side draft-draft?
Rocket

 

[firstturn]

Actually Rod I'm sooo impressed (or hurt) that we have so many gear heads out there(which is great) I have decided to move on to either Hiborn Mechanical Injection(HMI 101) with a Modern Touch of Computerized(HMI 102a)  or discuss my work or my latest find a original twin carburetor 100 Berkshire.  Thanks for the Flash Back or nightmares from the past.

Ron Carbaugh

[dsklcsw]

Thanks for the responses.  The bike will not idle with the choke on.  The bike has never idled.  I did clean the carb, but I will do it again.  With a larger pilot, the air screw doesn't do anything, which led me to believe that it was too rich.  Does anyone have any experience with Mikunis on 250 pentons?  The carb is mounted at what I feel is an extreme angle forward, do you think that I should adjust the floats differently?  Does anyone have an intake manifold and a 36mm Bing that they want to get rid of?  

Thanks for all the responses so far,
Dwayne



 

[Mike OReilly]

I'm not sure why no one else has suggested this (I guess they're too busy talking about Webers; side-draft vs. down-draft etc.), but you're problem sounds like a classic air leak situation. If you have a 250 with a #20 pilot jet, and a #200 main, something is really wrong. (Stock is a 35 pilot and a 165 main).
I strongly suspect that you have an air leak somewhere in the area of either the intake manifold, or the crank seal on the mag side (And I would suspect the mag seal in particular).
The solution is to take either Quick-Start or WD40, and while the engine is running, spray it at those areas. If there is a leak, the intake vacuum will suck those fluids into the bottom end, and you the RPM will rise noticeably.
Give it a try and keep us posted.
Mike

 

[Rocket]

Mike
Dwayne has a Mikuni carb, so your stock sizes are for a Bing, not for a Mikuni.  Usually if you have a crank seal leak on the mag side, it will be running extra lean all the time.
Rocket

 

[t20sl]

You might check and see if the needle jet is in upside down.  This is the jet that the needle slides up and down in.  Don't know much about mikuni but this can happen in some Kehin (Honda) carbs where main jet holder and needle jet are 2 seprate pieces, causing rich condition at very slow engine speeds.