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Post by RapidJim on Nov 9, 2014 10:53:12 GMT -5
I got an interesting phone conversation last week concerning a customer doing his own valve adjust. After he adjusted his valves, he told me his 300 trike would turn over really fast but would not start. He said he went back and checked it again, with the same results and wanted to know what I thought. He told me how he adjusted the valves and it was the correct proceedure and gap. I asked him if he could do a compression check and he said he didn't have the correct adapter for his gauges and wondered if I would take a look. About an hour later, he showed up with his Magnum on a trailer. We unloaded it and bought it in the shop. When I attempted it start it I could tell by the way it was turning over that there was zero compression. So I did a leak down test and had air coming out of the carb, hmmm did he clip the intake valve? As I was removing the intake valve cover, to inspect the rocker, I heard a snap noise. Didn't really pay to much attention to it at that moment. Checked the lash and it was correct. Rotated the motor to watch the rocker movement and at this time we had compression. I removed the leak down tester and verified compression. Now I am puzzled. Look into the intake valve side with a flash light and didn't see any junk inside. As I picked up the valve cover, it slipped out of my hand, when I picked it up this is what I saw  It appears that the oil deflection flashing was holding the intake valve slightly open. Unlike the exhaust valve cover which has 3 bolt holes and can only go on one way, the intake valve cover has 2 bolt holes and will fit either way. I have not had this happen before, and never looked at the valve cover, must have been lucky each time or maybe this is only this way on the newer motors. Whatever the case, I thought it would be worthwhile to make a post so it don't happen to others. Or if it does they know what to do. |
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Post by alleyoop on Nov 10, 2014 0:24:23 GMT -5
WOW!! Great Find Jim that is weird and who would of thought of anything like that causing loss of compression due to that piece on the inside of the cover not allowing the valve to completely close.
Alleyoop
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Post by RapidJim on Nov 10, 2014 9:41:36 GMT -5
Yep one for the books. That is why I took the time to post it so others don't have the same hair pulling experience
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Post by wheelbender6 on Nov 11, 2014 19:17:06 GMT -5
Great tip. You have saved many people from a top end tear down.
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Post by mrx2002 on Nov 17, 2014 1:02:19 GMT -5
Yep that would have been my next step is to pull the head! Haha i can see it now pulling the valve cover and ripping everything apart to find nothing wrong. Good tip man!
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Post by RapidJim on Nov 17, 2014 9:10:32 GMT -5
Thanks guys!
I was working a Hisun UTV last week and the valve covers for it have the same deflector in both the intake and exhaust, however on that motor the cover only goes on one way.
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Post by 4950cycle on Nov 22, 2016 18:19:00 GMT -5
Yep one for the books. That is why I took the time to post it so others don't have the same hair pulling experience JCL MP250A Lihai 257cc powered / I know this is an old thread, But does anybody know by now if the older 2007 257cc Linhai scooters had this same oil deflecter on the inside of the intake valve cover ? |
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Post by bob123456789 on Nov 23, 2016 12:38:20 GMT -5
4950cycle. Seeing your post made me wonder the same thing. I just happened to have both valve covers off my Linhai 257 right now. Both the intake and the exhaust look like they have the ridge. The intake valve cover looks like it can be put on either way. I will be watching this very closely when I put it back together. I am guessing that having the ridge on the side away from the nut is correct. Am I right about that? Thanks very much for pointing this out.
RapidJim. Thanks for looking out for everyone else and putting this post up here a while ago!
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Post by crawford on Nov 23, 2016 13:21:15 GMT -5
this is my main concern about everyone saying about always checking checking valve lash myself I believe in old school compression test will tell a great deal about valves and rings. Then make a intelligent way to go if compression is great leave it alone. The old saying is still right if not broke leave it alone.
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Post by 4950cycle on Dec 14, 2016 18:25:42 GMT -5
JCL MP250A Lihai 257cc powered / Still havn't taken mine off (. Thanks for telling me I probably have the ridges in my 06 257cc Linhia.
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Post by rockynv on Dec 20, 2016 4:36:35 GMT -5
this is my main concern about everyone saying about always checking checking valve lash myself I believe in old school compression test will tell a great deal about valves and rings. Then make a intelligent way to go if compression is great leave it alone. The old saying is still right if not broke leave it alone. Compression can be a tad high if the valves are excessively loose and you can experience excessive oil consumption from the valves closing too early from being too loose. If the valves are slightly tight you may not notice until after the valves have burned and cracked from the shortened amount of time they are in contact with the valve seats and getting cooled. Best is to check the valve lash per the maintenance schedule published by the manufacturer and pay attention to reassemble things as you found them. A marking pen and digital camera can greatly assist in doing this right. I keep an old cell phone for use as a shop camera which works out famously. They work just fine on your wifi just like any other personal computing device and your main cell phone stays clean and grease free. |
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Post by crawford on Dec 20, 2016 20:20:10 GMT -5
Newer happen compression doesn't go higher if rocker is a little loose. Valve is closed it's closed it can't close any more then that... A compression tester is a basic tool but any buddy who services engines should have one and know how to read one. To many people think you can you your finger this is a joke a best you need fuel,compression,fire if you missing something it's not going to run. In some cases will run but poorly at best.
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Post by rockynv on Dec 21, 2016 12:54:55 GMT -5
Newer happen compression doesn't go higher if rocker is a little loose. Valve is closed it's closed it can't close any more then that... A compression tester is a basic tool but any buddy who services engines should have one and know how to read one. To many people think you can you your finger this is a joke a best you need fuel,compression,fire if you missing something it's not going to run. In some cases will run but poorly at best. If the valve is too loose it closes too early during the intake stroke creating a partial wet lock as excessive amounts of oil are drawn past the rings which on the compression stroke causes higher than normal compression. That is why engines with valves way out of adjustment will at times suck all the oil out of the crankcase if very short time. Seen this play out multiple times with folks thinking they needed to rebuild the cylinder when all they needed was to take care of a past due valve adjustment. |
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Post by crawford on Dec 21, 2016 13:13:02 GMT -5
If still won't happen not in a million years your using government fuzzy math in you mind.
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Post by rockynv on Dec 22, 2016 0:33:57 GMT -5
If still won't happen not in a million years your using government fuzzy math in you mind. No math just 50+ years of real life experience. Excessively loose valves close too early along with open too late on both the intake and exhaust stroke and while you may not see the effects during a compression test while cranking the engine at low speed the results at high speed and under load are higher oil consumption and increased blow by. Valve lash being too loose or too tight impacts the duration of how long the valves stay opened or closed with excessively loose leaving the valves closed too long reducing how far they open impacting intake and exhaust efficiency while too tight will cause them to stay closed for too short a duration with the potential for burning the valves and damaging the valve seats along with poking a hole in the piston and scoring the cylinder if the valve head shatters or breaks off after getting overheated. Bottom line is follow the service schedule and check the valve lash per that schedule regardless of what shortcuts others endorse. Don't wait until things have gotten so far out that they show up during a compression test as too often some level of damage will have already occurred. |
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..BAD TO THE BONE..
