1340 stopping when intake leak testing

[xlfan]

When spraying flammables at intake seals, engine is stopping. Can anyone explain that? When taking off the vacum hose at petcock and spraying directly into hose, an immediate stop occur. Why? What is happening?

xlfan

[mkd]

xl! i'm guessing the vacumn port you are removing is shutting the fuel petcock off. my 98 springer fuel petcock has a diaphragm that needs vacumn to keep the fuel petcock open. if the bike kills there is no vacumn so the fuel petcock closes. it's a safety thing. i'm guessing your bike has the same type fuel petcock so when you remove the vacumn line the fuel line instantly shuts off because it needs vacumn to stay open.

[98lowrider]

The vacuum line from the carb goes to the petcock and the voes switch. At idle voes disconnected it will stall out. That line is only for pulling a vacuum on the petcock and voes.   

[JBarrettB]

I use brake clean to check for leaks, very flammable, but it will kill the motor.
It takes and open flame to make this brake clean burn a spark or an ember will not ignite it. For example if sprayed on a lit cigarette it will put the cigarette out not erupt in flame. 
The vacuum line being removed will stop fuel flow from the petcock but the bike will continue to run for a short time until the fuel in the float bowl is depleted.

JB

[Hossamania]

Use carb cleaner instead. If the motor is dying when you spray the brake cleaner at the intake seals, they need to be replaced.
Make sure you're not getting over spray into your carb causing a false reading.

[xlfan]

I'm on the 4th set ofintake seals now, intake and flanges have been checked for cracks and other irregularities, flanges slightly ground down, seals soaked with WD40, silicone spray and now last Hylomar. I'm beginning to think there must be something other than intake seals.

Why would engine kill instantly when flammable sprayed directly into vacum hose at petcock end (petcock bypass vacumed by vacum pump)?

xlfan

[Old Crow]

I understand what you're doing spraying around the intake seals, but what are you trying to accomplish by spraying into the vacuum hose?
Since that is manifold vacuum to that hose, you're shooting a spray of straight, non-atomized, liquid into the intake after the air has already been saturated with fuel while passing through the carb. 
In effect, you're flooding the engine out.

Now, if it stalls when you spray it around the outside of the intake, that's a different can of fish.  I always remove the air filter cover when doing this.  Makes it easier to avoid the carb sucking up the fumes through the front and giving a false reading.

[92Fatty]

Is this a stock cv and factory intake? I'm just wondering about a part mismatch. I swapped intake seals on mine with the carb attached trying to hurry and they leaked. Maybe I tried to force or something. It was much easier installing intake with carb off of it.

[xlfan]

Update
Replaced vacum membrane in petcock with a vacum bypass, new vacum hose from carb to VOES. No change.
Discovered slightly cocked intake flanges, changed them and intake leak was gone when cold, went for a testride and leak was back, also when cooled down and restarted.

Is it possible that heads could be mounted in opposite directions so the distance on one side of intake manifold will be too far from head gasket flange?

xlfan

[mkd]

i would think that could be possable as well as the carb mounting bolts could be pulling the intake seals as well. it's best if the intake is mocked up loose enough to mount the carb and everything gets alligned then tighten the intake bolts.

[ramcr913]

xlfan- is the manifold a stock one or aftermarket? Is there an excessive amount of space between the manifold and the heads?

[dakota224]

Get NEW flanges & NEW seals & you should be good t go..

[xlfan]

The last atempt was with new flanges and gaskets, didn't leak at startup, began leaking when warm, stayed leaking again, also after cool down and restart.

Stock CV and manifold. Stock cyls. and heads. About 0.080'' space on each side of manifold, too much in my opinion, but all stock so what can be done about it?


xlfan

[Hossamania]

If there is excessive gap between cylinders and manifold, for whatever reason, you may have to change manifolds to a little wider one. I am not sure what is available, but maybe S&S or Mikuni has one that is slightly wider to take up the gap.
Have you tried new flanges?

[nibroc]

most of the time those wider manifolds have to be filed to fit properly

[xlfan]

New gaskets, new flanges, new intake manifold. This is the most stubborn intake leak I have ever seen. Finally was able to get rid of the leak by building a new base with silicone on the outside. This is NOT how it should be 

Have anyone else EVER experienced this on an EVO?

xlfan

[nibroc]

only stroked ironheads

[xlfan]

Thanks all.

Finally no intake leak, but bike still has exhaust (it's not non-baffled drag pipes) backfiring when you let off throttle, not as bad as it was with intake leak though. Even another CV are on the bike now, in order to try and rule out problem sources. Can this condition be caused by ignition module or VOES?

xlfan

[98lowrider]

Voes works at idle and shuts down once vacuum gets to the spot it's set at. I would say no. If your voes wasn't working you wouldn't idle it would stall. You can check it by unplugging it and testing for ohms across the two pins. Has to read less that 1 to be good should be zero. You'll probably need a second set of hands as it will keep stalling on you when it's not plugged in. It will be and open circuit at idle then should close when rpms go up and reading will go to zero.

[djsim]

If I read right, brake cleaner was used to check for intake leaks...not good, I read an article a while back maybe on this site that brake cleaner when ignited can produce phosegene gas...very deadly even in small amounts, thus if there is an intake leak it will be sucked in, combusted and exhausted and if there in inadequate air... well read up on this its not a pleasant death. Use carb clearner , wd 40 just not brake cleaner.

[hogpipes1]

My fav for leaks is a propane tank with tip off and rubber hose over the end. Hose with low pressure  can be move around the flanges.  High  temp RTV is good ins.

[vincer77]

If I read right, brake cleaner was used to check for intake leaks...not good, I read an article a while back maybe on this site that brake cleaner when ignited can produce phosegene gas...very deadly even in small amounts, thus if there is an intake leak it will be sucked in, combusted and exhausted and if there in inadequate air... well read up on this its not a pleasant death. Use carb clearner , wd 40 just not brake cleaner.

This was interesting so i did some looking into it.  Chlorinated solvents can produce phosgene gas when heated.  I just checked a can of Wearever Brake Cleaner i have and it is non-chlorinated and I suspect all that you can buy at the auto parts store is non-chlorinated these days.

[Hogman]

If I read right, brake cleaner was used to check for intake leaks...not good, I read an article a while back maybe on this site that brake cleaner when ignited can produce phosegene gas...very deadly even in small amounts, thus if there is an intake leak it will be sucked in, combusted and exhausted and if there in inadequate air... well read up on this its not a pleasant death. Use carb clearner , wd 40 just not brake cleaner.

This was interesting so i did some looking into it.  Chlorinated solvents can produce phosgene gas when heated.  I just checked a can of Wearever Brake Cleaner i have and it is non-chlorinated and I suspect all that you can buy at the auto parts store is non-chlorinated these days.

That's what used to scare me when we were checking for Refrigerant leaks Years ago. Generous Motors Sent us an "Essential Tool" to do it. A Damn Propane TORCH! Yes, it was Lit while Checking for leaks.......  For the newer guys doing today, I'm GLAD they have Much better Technology available to  do the Checks. I HATED Having to check for leaks that way....