37 UL engine hesatation

[ldfly112]

been riding my 37 UL for aprox. 900 miles since total rebuild engine starts 2 prime kicks then starts next kick every time. throttle is very responsive but hesitates when holding the throttle steady.but always acelerates well I have installed the ebeyond 2000 elec. ignition in the distributor. have been adjusting the M51 linkert carb. since the beginning.Even tried a second carb. anybody have any suggestions on how to get rid of the hesitation

[duffeycycles]

Possibly overcharging because cutout is not working right.Check voltage when running & revved up

[T. Cotten]

I've got no clue about your "distributor", ldfly!

But please make certain your idle is fast enough to smooth out when advanced.

Potato-potato is too slow, producing a 'flat spot' when the venturi isn't ready to kick in,..

And carb borewear from the throttledisc may require an even faster idle.

....Cotten

[ldfly112]

I am still struggling with engine running rough still starts easy. One thing that is happening also is the distributor . I retard it to start and when it starts i advance it when you change the distributor from retard to advanced the motor sounds the same at both locations yet i can see the timing mark on the flywheel move as it should when using the timing light. should this be telling me something about the timing or the distributor any suggestions

[kitabel]

How mucu spark advance range between retard and advance positions?
If they're too close together, idle may not change much between the 2.
If I had a manually adjustable breaker:
idle 10 BTDC
advance mechanism adds 20 degrees
full advance 30 BTDC

[T. Cotten]

I've never ever found a distributor on an HD, Idfly!

But if you can lock it down with the line in the middle of the hole at full advance, I'd leave it there.

If advancing and retarding does not change the idle, something else is controlling it.

(Maybe the electronic gismo?)

....Cotten

[dukekleman]

You stated you can verify timing advance and retard movement with a timing light at the flywheels. Your question is then that you can't audibly hear the normal RPM rise with timing advance, correct?
IF this is the case, your carburator settings are the issue. An overly rich air fuel ratio will not respond to the timing advance like your accustomed to. It will also always cause the hesitation you described. Most likely your throttle disc is opened to far at idle due to the richness. This will cause the plate to expose the transitional ports and inturn cause the hesitation. Of course there are other carburetor/manifold items that can cause this issue as well, but it's my belief it's all in the fuel system causing this issue.

[ldfly112]

Thanks Dukekleman I have tryed adjusting the M51 linkert . When turning in the low speed jet completely it does not change how the engine is running. what are your thoughts thanks helping

[T. Cotten]

It certainly shouldn't even run shut, Idfly!

The length of the LS needle from the bottom of the knob (above the threads) to the point should be ~3.670".

Please be certain the spring in the knob rebounds, and the spring collar is in place beneath the lift lever spring, with the 'top hat' upward to center the spring.

The most common cause for an extremely rich mixture is the motor won't run any other way.

....Cotten

[dukekleman]

So it is indeed to rich on fuel mixture.
1) Have you verified the proper fuel height and control operation of the Needle/Seat and Float assembly?
2) Is the low speed needle correct for it's application, assembled correct, needle taper smooth and fully seat when turned all the way in?
3) Any chance someone has modified the transitional holes and slot in the past when trying to clean the carburetor?
4) Are all high speed components installed and enlarged from someone in the past?

[T. Cotten]

So it is indeed to rich on fuel mixture.
1) Have you verified the proper fuel height and control operation of the Needle/Seat and Float assembly?

Got a glass bowl, Duke?

2) Is the low speed needle correct for it's application, assembled correct, needle taper smooth and fully seat when turned all the way in?

I believe it should seat before it is turned all the way in. That's why there is a spring in the knob...
(A 'dry-erase' marker on the tip will give a good reading of contact.)

3) Any chance someone has modified the transitional holes and slot in the past when trying to clean the carburetor?

*Gasp* Can you believe they are actually reproducing the torture drill kits?!?

4) Are all high speed components installed and enlarged from someone in the past?

Please explain "enlarged" Duke!
(Thanks in advance,...)

....Cotten

[dukekleman]

I've run across main jets that are marked a particular size but have apparently been cleaned with drill bits or the dreaded torch tip cleaners. Verification of number labeling on the jet can't be trusted.

[T. Cotten]

I've run across main jets that are marked a particular size but have apparently been cleaned with drill bits or the dreaded torch tip cleaners. Verification of number labeling on the jet can't be trusted.

Especially with modern repop jets, Duke!

Not sure any are 'right'. (Good thing Idfly's M51 didn't use one.)

Since he swapped another carb without result, its probably something else maybe.

Carbs are damn forgiving or I would never have messed with them. Assuming valve adjustment and all other things are in order,... Air has to be getting in somewhere, and it don't take much.

....Cotten
PS: I'm guessing that Ebeyond is a Hall-effect replacement for points; If its anything more than that, all bets are off.

[ldfly112]

After disassembling the carb. and reading the palmer book it was found that the low speed needle was to short. switched it with a longer version. fired right up adjusted carb. and timed it mark dead center with full full advance . The engine runs very close to perfect . I had no idea that there were 2 versions of the low speed needle until reading it in the palmer bible . THANKS to all who have tried to help

[dukekleman]

Glad you had success in diagnosing the problem. Happy and Safe riding!