I recently worked on a friends Raptor that lost power. I ran a compression check and it was low (145psi). The motor does not have many hours on it. I removed the cylinder head cover and found that the DECOMPRESSOR CAM GUIDE PLATES were not installed when the last person worked on it. Does anybody know what function these plates have? Could this cause a loss of power? I did not do the oil test because I was removing the piston anyway to switch to a higher compression setup. BTW the rings were worn and I know that would be the main cause of the low compression. I will be installing new guide plates but I still want to find out if anybody knows what they do and if they are needed.

 

I would think that they should be there to help protect the weights from the centrifugal force that would be present when the engine is revved up. The pins would be taking some abuse without the guide plates. JMO

 

How do you do away with the decompression all together?

 

Vilnrk, would there be a chance that compression is being lost with out the guide plates while running?

 

RRC is it possible that your timing was off with out the plates? If the cams guides were not there then the chain was loose and enough action could cause the cams to jump a tooth. When Dustys was off he had the same power loss problem. The valves could still be open when the compression is building.

 

<< How do you do away with the decompression all together? >>

 

my DS had the decompressor to hang on it. it lost alot of power. we removed it completely. it still strats easy and haven't had any more problems. if it was doing the decompressing thing while it was running the plugs would have look lean. we melted my plugs til we figured it out.

 

read this post.

 

RaptorRRC - no. The only way you would have a loss of compression is if (they) didn't get the dot on the decompression device aligned up with the other 3 dots on the cam when (they) installed the gear back on. I actually did this on my raptor. I timed up the cam but didn't notice the dot on the decompressor. I had it 180 out. It will start and idle normal. Now when you hop on it for a test ride you will notice that all the sudden there is a loud noise comming from the engine. It sounded like a very loose rocker to me. If you are experiencing this then you should take the top off and spin it over to see the 3 dots on the cam and the 1 dot on the decompressor should be to the 12:00 position. If it is at the 6:00 position (hahaha) then you found the problem.
Hope I help you out [img]i/expressions/face-icon-small-smile.gif[/img]

 

Thanks for the replies. I figurewd out how it works shortly after my first post. The guides do very little but if I had them I would use them. The decomp system on the Raptor has nothing to do with cam timming. It just has a pin that hits the right exhaust valve opening it until the motor starts and then centrifigal force opens the weights and pulls the pin back into the cam. The decomp system can easily be removed if you wanted to.