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Post by johnh8402 on Aug 10, 2010 1:10:03 GMT -5
Hi all I am new here and I was wondering if someone can help me with this. Before my moped broke down, when I would accelerate the spark plug cap would fling off in mid throttle, kinda like there was to much compression (I wonder if that is even possible). So I would have to stop on the side and put it back on, only for it to do it again. I got tired of the stock plug cap doing this so I went and bought an after-market spark plug cap from Checker Auto Parts. The spark plug cap stayed in place now.
It was running fine for a couple weeks, then it just stopped working. When I would try to start it would not start at all. For some strange reason it was not pulling any air from the intake, so no vacuum for the vacuum line. I thought it may be a piston problem or leaking head or base gasket. So I pulled off the head, the cylinder, put on new gaskets, only to find out it was still doing the no air thing. So again I pulled off my head, cylinder and now piston this time. I took it to a shop they looked at the piston and the cylinder and head and said it looked fine. So again I bought new gaskets put everything back on correctly with the arrow on the piston facing the exhaust port. Put the gaskets on and torqued the head nuts to 160 in-lbs or 18Nm.
When I check for compression I am getting 75psi from the electric starter and about 65psi from the kick starter. Still no air is being sucked in.
Any and all help will be greatly appreciated on this.
Thank You for your time and effort.
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Post by 2strokd on Aug 10, 2010 7:49:57 GMT -5
Welcome!!!
Does it have spark???
Hhm, its a shot in the dark, kinda..
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Post by 90GTVert on Aug 10, 2010 7:53:24 GMT -5
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Post by stepthrutuner on Aug 10, 2010 8:58:30 GMT -5
You could have a crankcase leak at the bearing seals or where the 'halves' meet or at the intake/reed mount. This would account for both loss of vacuum and loss of compression.
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Post by johnh8402 on Aug 10, 2010 12:44:23 GMT -5
Yes it does have spark. The shop I did take it to the owner said the piston rings looked fine. Are the bearing seals the oil seals( Right Crankcase Oil Seal)? What kind of Gasket sealant can I use for the two halves of the crankcase, because I noticed it was not a paper gasket but some silicone??? material. So the best way to check if it is vacuum / compression loss is to do a leak down test correct. I guess I have to wait to get paid again in two weeks. OH also I forgot to mention that the engine is a 1PE40QMB not the standard 1E40QMB |
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Post by 190mech on Aug 11, 2010 19:48:07 GMT -5
Might take a look at the reeds too...
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Post by 2strokd on Aug 12, 2010 7:53:21 GMT -5
The stuff between the case half is a type of epoxy. You can get away with using
different brands and such but DONT use anything that gas and or oil with eat away.
I personally havent had the pleasure of tying a motor back together but others here
have, maybe one of them can chime in and give more advice.
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Post by 2strokd on Aug 12, 2010 7:54:18 GMT -5
A leak tester can be a 2T tuners best friend!
A must when building a motor
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Post by andsetinn on Aug 12, 2010 18:16:39 GMT -5
This is interesting. I've had spark plug leave the engine when running but never spark plug cap. Could the engine be loose and somehow pull the cap off?
You're sure it gets spark? Did you replace the spark plug when you replaced the spark plug cap. I've known replacement caps to fail, under some circumstances they don't make contact with the plug wire when they're installed but work fine when the spark is checked with a plug.
I'd check for obstruction in the exhaust, did someone put a potato in it? Then the intake, check the reed valve, carburetor. Try bypassing the fuel valve or open it manually using syringe on the vacuum line.
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Post by johnh8402 on Aug 13, 2010 2:31:53 GMT -5
Yes it does have spark.
I found that part very interesting as well. The spark plug cap would fling off in mid throttle. No joke. The engine is not loose, the spark plug faces forward like all the minarelli horizontal type engines. I have the 1PE40QMB instead of the norm 1E40QMB. All mine is just shorter transmission case. The fact that the spark plug cap would fling or "pop" off is still the same.
I noticed something different than most other engines of the 1E40QMB model. My cylinder has a double step from the crankcase rather than single straight steps.
Also if it is a seal leak somewhere. How would I go about finding it without a Leak Down Tester
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Post by Goosey on Aug 13, 2010 3:36:06 GMT -5
There isn't a leak around the spark plug threads? That would take a lot of pressure to blow off the cap if that's whats happening.
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Post by johnh8402 on Aug 13, 2010 14:08:57 GMT -5
It doesn't feel like the is air escaping from the cylinder around the spark plug. But still that doesn't explain the lack of vacuum from the intake. This problem is really weird.
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Post by johnh8402 on Aug 21, 2010 3:30:29 GMT -5
UPDATE!!!
Ok I found the problem. The problem was loose left crankshaft oil seal. I guess it popped out because of the high compression as to why the plug cap was blowing off. This was the cause of the loss of vacuum from the intake as well as the low compression.
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Post by 190mech on Aug 21, 2010 20:07:41 GMT -5
Glad you found it!Hope its running well now..  |
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Post by Fox on Aug 21, 2010 20:40:29 GMT -5
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