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Decompression cover 3 or 5 bolt

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Hello,

 

I tried to kick over my 1987 XR600R the other day and just heard a ton of air rushing out somewhere.

 

Found it to be the decompression chamber. The cover was leaking around the bottom edge. When I took it off today I found that I have a 5 bolt head and 5 bolt gasket, but my cover is 3 bolts. Probably the reason its leaking, as theres two bolts less to apply pressure. 

 

What year XR started using the 5 bolt cover? So I can find the right model to take it off.

Thanks!

 

IMG_7712_zpsxjnxycjq.jpg

 

IMG_7711_zpsjhids4al.jpg

 

IMG_7713_zpsgl3l7kyg.jpg

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is it possible to drill out 2 additional holes? if not and you cant find the right cover, permatex makes great stuff gasket maker. ive used lots of times with excellent results.

Edited by garthr

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A 3 bolt cover on a 5 bolt head is normal, heres one off my shelf from an 87xr6 that was never messed with. On an 87 xr600r, this cover doesent do anything. The space behind the cover is just void and is not connected to anything at all because the decomp is on the right exhaust valve only. Notice the color of my head vs yours, now look at the cover on a 5 valve xl600r motor.1452967285017.jpg

Your bike has a 5 valve xl600r motor, not an xr600r motor and someone has put on a later 4 valve head cover plate. Most likely the 5th (decomp) valve is leaking causing your problem. You may find an issue with the auto decomp cable from the kicker is causing the valve to stay open or you may have to pull the valve cover and inspect the 5th valve. You also need a cover from an xl, ebay is your friend.

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Only the early XR/XL's (83/84) used that chamber as part of the decompression system. By 1987 Honda went away from that. If you look at a XR600 parts fich you will see the head has five holes but the cover only three. Your air leak is from somewhere else.

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Only the early XR/XL's (83/84) used that chamber as part of the decompression system. By 1987 Honda went away from that. If you look at a XR600 parts fich you will see the head has five holes but the cover only three. Your air leak is from somewhere else.

His motor is an 83 or 84 xl. The air leak is probably the decomp valve.

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Really???

Says 1987 XR600

yeah, read the other thread he started. says the po "used xl600 parts on the motor" but it has the old XL black engine enamel and it is blowing out the 5th valve chamber cover.

looks like a duck, quacks like a duck.......

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So now I'm supposed to know of another thread? Bugger off.

Hold your thumping horses guys! No need to fight! I did ask in two different threads, sorry to confuse you, my bad! I really appreciate you both take the time to help me out here.

 

I explained that its an xl head in post number three of this thread. Sorry if I was unclear.

The op just didnt know what he had.

It turns out the entire engine is indeed all 1987 XR600R with the exception of the carbs and clutch. This is according to the PO. The 87 apparently had the 5 bolt head, but a 3 bolt cover, I also have the decomp at the kick and handlebars. Is this possible with what you see or are the models so similar it is near impossible to judge by eye?

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Hold your thumping horses guys! No need to fight! I did ask in two different threads, sorry to confuse you, my bad! I really appreciate you both take the time to help me out here.

It turns out the entire engine is indeed all 1987 XR600R with the exception of the carbs and clutch. This is according to the PO. The 87 apparently had the 5 bolt head, but a 3 bolt cover, I also have the decomp at the kick and handlebars. Is this possible with what you see or are the models so similar it is near impossible to judge by eye?

Sorry about that, I wasn't trying to offend anyone or start trouble.

An xr head will have both the handlebar and kicker decomps but the two cables will hook to the same lever near the right exhaust valve on the right front of the motor.

The XL head in question will have the same two decomp cables, one from the handlebar and one from the kicker. the difference is that the kicker cable will go to the back of the motor above the carbs. If your bike has this setup it is definitely an XL head if not whole motor. You may need to pull the tank to verify cause its kinda hard to see.

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Sorry about that, I wasn't trying to offend anyone or start trouble.

An xr head will have both the handlebar and kicker decomps but the two cables will hook to the same lever near the right exhaust valve on the right front of the motor.

The XL head in question will have the same two decomp cables, one from the handlebar and one from the kicker. the difference is that the kicker cable will go to the back of the motor above the carbs. If your bike has this setup it is definitely an XL head if not whole motor. You may need to pull the tank to verify cause its kinda hard to see.

If the cable is routed & used as the 5th valve XL set up, is it possible to disconnect the cable to the 5th valve & convert to the external valve set up like the XR head has, if the little bell crank is obtained? The reason being, some had said the 5th valve is a potential leak point for compression? So if it sealing good now, then  conversion  might keep it that way?

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If the cable is routed & used as the 5th valve XL set up, is it possible to disconnect the cable to the 5th valve & convert to the external valve set up like the XR head has, if the little bell crank is obtained? The reason being, some had said the 5th valve is a potential leak point for compression? So if it sealing good now, then conversion might keep it that way?

Yup, but the problem is that his is already leaking (unless the cable is sticking).

I know some guys remove the valve and weld up the hole.

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I was talking about my project, for future prevention. & I didn't want pull apart head to weld up if I didn't have to.(afraid of the stripped out thread syndrome)

Thanks

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Sorry about that, I wasn't trying to offend anyone or start trouble.

An xr head will have both the handlebar and kicker decomps but the two cables will hook to the same lever near the right exhaust valve on the right front of the motor.

The XL head in question will have the same two decomp cables, one from the handlebar and one from the kicker. the difference is that the kicker cable will go to the back of the motor above the carbs. If your bike has this setup it is definitely an XL head if not whole motor. You may need to pull the tank to verify cause its kinda hard to see.

All good!

 

The kicker cable does end up above the carbs, so I guess it is an XL head, curious to see what the rest is. Frame is '87 XR600R, because thats what the rego says.

 

I'm going to disconnect the cable from the kick and see where we end up, if not, I'll take the head off and weld the valve shut.

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If the cable is routed & used as the 5th valve XL set up, is it possible to disconnect the cable to the 5th valve & convert to the external valve set up like the XR head has, if the little bell crank is obtained? The reason being, some had said the 5th valve is a potential leak point for compression? So if it sealing good now, then  conversion  might keep it that way?

Simple answer is yes.

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The kicker cable does end up above the carbs, so I guess it is an XL head, curious to see what the rest is. Frame is '87 XR600R, because thats what the rego says.

I'm going to disconnect the cable from the kick and see where we end up, if not, I'll take the head off and weld the valve shut.

You can also look deep into the decomp chamber to tell if it's an XL600 head. XL heads will have the passage drilled to the 5th valve while XR heads are blank as cast chambers. Was hoping to see that in your picture but it's just too dark to tell. That's easier to check than the cable/lever connection point. 83/84 XL600s and XR500 both came with the 5 bolt cover but only the XLs had the extra valve and passages. I can't recall which setup 85-87 XL600s had. The valve leaks usually because spring pressure is just too light to seal the valve if the seat gets carboned up at all. Lapping the valve and installing a stiffer spring will suffice for the welding. Then change to the exhaust valve actuated decomp leaving the XL 5th valve/lever assembly intact but inoperative. Edited by valvesrule
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