Author Topic: Sarahs Pilot Engine Troubles!!!  (Read 2768 times)

Niles

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Sarahs Pilot Engine Troubles!!!
« on: August 06, 2005, 03:11:52 PM »
I am gonna post this in several places just so it gets seen.  Hope that doesn't upset anyone.

So we went riding today and we rode about an hour when I pulled up to Sarah and she said had back to the truck. When we got back to the truck she said it died on her if she ever slowed to an idle and she had to pull the choke to get it to start again. So I crank it up and rev the engine a few times and the engine just starts running wide open. I flip the off switch and take the key out still running full RPMs!!!!! Finally I pull the choke and it quit. Haven't cranked it again. Immediately loaded it up and came home. Anyone got any ideas?? Thanks for any help... as all of you know I am a pilot newbie!!

Thanks
Niles

ludedude

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Sarahs Pilot Engine Troubles!!!
« Reply #1 on: August 06, 2005, 04:18:25 PM »
I'm sure others will chime in soon, here or elsewhere.

Here's my take on it. You have an air leak on Sarah's engine somewhere. (carb intake, head or base gasket). With an air leak, you have the chance the engine gets into a runaway state as you experienced. It can suck more and more air as you havenot control to shit the supply of air off as you have when its sucking air through the carb as it should....when it does, you close the throttle and starve off the air and the engine idles down. With a leak it can take off on you. The air leak, leans the fuel/air mixture way out, hence the reason it would run woth choke on...the choke closes off the air flow, combating the air leak supply of air.

Time to pressure test the engine before you do anything else.

Niles

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Sarahs Pilot Engine Troubles!!!
« Reply #2 on: August 06, 2005, 05:48:23 PM »
Not that this means anything but I did do a compression test and it is around 140-142 on her stock engine.  Now how do I go about doing a pressure test??  Remember I am a newbie so talk to me like I know nothing cause I don't  :)

ludedude

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Pressure testing instructions, how to pressure test
« Reply #3 on: August 06, 2005, 07:50:43 PM »
Cool, compression is good. You'll need some odds and ends to make a pressure tester. There's a few different ways to build one, but basically they all work the same. Block off all intake and exhaust paths and add air, Watch t o see that it maintains ~7 psi for 5-7 minutes, if not use soapy water to find where the air is escaping. This will be the spot air is entering when running ;)

I'll describe mine. In the photo (sorry, that's all I have...for now) you'll see the exhaust block off plate. ...OK steps first.

1. Remove exhaust pipe
2. remove carburetor (pull the carb from the rubber intake boot...leave intake on cylinder)
3. remove air pulse line (air line from fuel pump to cylinder) from fuel pump end.

Now, you need to block all of the above, and add air into the engine through one of them, with an air gauge on it.

Back to describing mine. I made and exhaust block off plate. I remove the exhaust and the exhaust manifold (three bolts holding the manifold "ring" to the cylinder that the exhaust mounts on). I then bolt on the exhaust block off plate with a thin piece of rubber between the plat and the cylinder (inner tube type rubber). My plate has a threaded hole in the center to which I have plumbed a "T" into it, from there I added a pressure gauge, and a schrader (tire stem valve) valve on the other leg of the "T". So this is my air entry and gauging point. I have made up an aluminum plug to go in the carb boot in place of the carb to block off that point. I leave the spark plug in. And I either fold the pulse line over and vice-grip   it or put a small bolt wrapped in Teflon tape into it. Then just use a hand pump and pump it up to ~7 psi and then watch and listen of leaks. Use a spray bottle with soapy water to locate the leak(s). Since Sarah's is stock and untouched, I'm guessing the rubber carb intake is old and cracked. But it could be the head gasket, base gasket, as well.

Now before I had those parts made I had used odds and ends previously, whatever works will work ;) A small bottle of STP Sun of a gun filled with water and frozen fits snugly into the carb intake boot :p You can get from plumbing stores expandable plugs to use in the exhaust manifold (leaving in place on the cylinder, compared to my method of removing it) and carb  boot. Then get fittings and plumb in a gauge and valve into the pulse line. As I said, whatever works, spray your plugs and fittings to ensure they're sealing properly.

Locate the leak and report back ;)

Tman

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Sarahs Pilot Engine Troubles!!!
« Reply #4 on: August 07, 2005, 02:58:19 PM »
Lude,
I know that this is probably the best method to check for air leaks, but what about PH's method with yours at CC... that is spraying WD40 around the block deal? As I recall, you found out pretty quick you had a leak.
Niles, I feel for you man... I s'pose pulling teeth would be easier  :P
ARNLFAER
(Another relative newbie looking for an easier route)

ludedude

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Sarahs Pilot Engine Troubles!!!
« Reply #5 on: August 07, 2005, 04:30:58 PM »
Yeah, I just don't like the run away engine thing :p Plus I like to actual "see" for sure where the leak is, WD-40 spray is good to indicate, yes there is a leak. Pressure testing with soapy water spray will let you pin-point the leak and see how bad it is, and see if there are multiple areas, as well.

Niles

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Sarahs Pilot Engine Troubles!!!
« Reply #6 on: August 07, 2005, 06:56:02 PM »
Here is a picture of the plug for the mean time while I get the stuff together to do a leakdown.

ludedude

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Sarahs Pilot Engine Troubles!!!
« Reply #7 on: August 07, 2005, 07:05:23 PM »
I "think" it's black? Can't tell from the picture...

Did I make it clear enough how to do a pressure test? Need anything else?

ludedude

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Sarahs Pilot Engine Troubles!!!
« Reply #8 on: August 07, 2005, 07:16:51 PM »
Do not take it aprt before you pressure test it...if you do, you ruin the "evidence" and loose the ablility to determine what caused it. Resist the temptation to pull the head off until  you get the pieces for a pressure tester and figure out where your air leak is (if there is one)  :)

tsutton44

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Sarahs Pilot Engine Troubles!!!
« Reply #9 on: August 07, 2005, 08:06:29 PM »
when you pull the carb for the leakdown test,look inside with a light and check the reeds.

Bucked

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Sarahs Pilot Engine Troubles!!!
« Reply #10 on: August 07, 2005, 08:51:34 PM »
A quick note to Niles - DO NOT over pressure your engine. In other words, when you do the pressure test, be absolutely sure you don't go over 10psi for testing. Anything above that could push gaskets out of the engine creating more problems.

I created a test kit with parts from Lowe's or Home depot. I'll be happy to take/post pictures of it all tomorrow. It included the following parts:

(I will update this if/when I find the sizes I mention are wrong)

1) A 1" PVC pipe end-cap used as a plug in the Carb boot. It is clamped into place with the carb mounting hose clamp.

2) A 1.5" rubber plumbing stopper to go in the exhaust flange. It is the kind that has a butterfly nut and bolt that allows you to tighten the butterfly nut to lock it in place.

3) A plumbing pressure gage on a brass "T".
3a)A barbed hose fitting on one side of the "T" going to the vacuum hose from the fuel pump.
3b)A shrader valve on the other side for adding air.

 I suggest using a air tank that you fill to 10psi max and use it to pressurize the engine. Using the tank will help ensure you don't over pressure the tank.

Niles

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Sarahs Pilot Engine Troubles!!!
« Reply #11 on: August 08, 2005, 05:28:31 AM »
Hey yeah Bucked Pictures of your set up would be great!!   I would greatly appreciate it!!  I am hoping this is a relatively minor thing that we can get fixed relatively soon, otherwise Sarah may just take MY pilot away from me to ride!!

Niles

ludedude

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Sarahs Pilot Engine Troubles!!!
« Reply #12 on: August 08, 2005, 05:34:34 AM »
Do you have a manual Niles?

tsutton44

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Sarahs Pilot Engine Troubles!!!
« Reply #13 on: August 08, 2005, 08:25:20 AM »

Niles

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Sarahs Pilot Engine Troubles!!!
« Reply #14 on: August 08, 2005, 10:17:04 AM »
Yep got a manual.  Thanks