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cam chain, camshaft, tappets, tensioner questions

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im helping my friend out with a few issues he's having with his japanese xr250. the motor is almost identical to the 96-04 250r. we took off the top of his engine head to look at a few things, as he's convinced he has a bad chain and tensioner.

 

issue 1: chain

 

he recently replaced his chain with a new one from a honda silverwing, but the mechanic removed a couple links from it because it was too long. does it look from the picture like it should, or does it seem like it is sitting too high on the sprocket?

 

20140608_185517_zps9197f089.jpg

 

we also want to know how much play is acceptable while its sitting on the sprockets with the tensioner engaged. is it okay that it moves a little from side to side when we shake it with our fingers? we have some videos that hopefully we;ll upload soon 

 

 

 

2. camshaft

 

does the camshaft look like its good shape?

 

20140608_162741_zps136df7d0.jpg

 

 

3. tappets

 

how about the tappets. do these look alright?

 

20140608_162643_zpsedaa2513.jpg

 

 

4. tdc bolt cover

 

is oil supposed to come out of this cover? we took it off to put it in tdc and oil just kept flowing out slowly.

 

20140608_182550_zpsae2bf8fe.jpg

 

 

5. tensioner

 

this bike has an automatic tensioner, the kind where to release it you need to push down on one rod while pulling up on another rod as is explained in this thread: http://www.thumpertalk.com/topic/902986-2000-xr250r-how-to-release-cam-chain-tensioner/ ... and NOT the kind you have to do manually as is the case with the xr400 i believe as is explained in this thread: http://www.thumpertalk.com/topic/771946-how-do-you-reset-the-cam-chain-tensioner/

 

so does this mean that once you replace the chain or sprockets or whatever you dont have to do anything else to get the chain to tighten up? he was hearing clanking noises and took it to his mechanic who said he reset the tensioner, but what is there to reset?

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#1
Maybe its just me, but that cam and chain do not look like they are meshing well together.

#2
The cam in that picture looks fine to me. The corresponding journals shown in pic#3 in the head cover look fine too.

#3
The rocker arm faces that ride on the cam look a little worn but hard to tell from a picture. On the far right one in the picture, is the wear deep enough to catch a fingernail on?

#4
Its normal to find oil inside the cover, but It should not pour out of that stator cover hole. The engine may have been overfilled.

#5
If you have access to a Honda shop manual, on page 7-5 it shows the tensioner. As the cam chain wears and becomes slack, the tensioner attempts to take up the slack by the spring pulling wedge "A" deeper into the unit. Wedge "B" locks "A" in place and prevents it from being able to loosen off on its own. Wedge "A" has to be released and pulled out/up (reset) when a new chain is installed.

Wedge "A" is pulled up and a pin inserted into it to hold it up while installing the chain and cam sprocket. Then the pin is removed and the tensioner finds its own equilibrium with that of the chain.



I don't know if you could even install a new chain of the proper length with the tensioner wedge all the way down. It would be trying to pull slack out of a new chain that doesn't have any and seems like it would make it very hard to install the cam sprocket.

XR250 tensioner.JPG

Edited by Trailryder42

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Is there any pitting in the cam on the shinny lobes or are they perfectly polished?  Things look pretty clean in there.

 

The chain looks wrong like you said.

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#1

Maybe its just me, but that cam and chain do not look like they are meshing well together.

#2

The cam in that picture looks fine to me. The corresponding journals shown in pic#3 in the head cover look fine too.

#3

The rocker arm faces that ride on the cam look a little worn but hard to tell from a picture. On the far right one in the picture, is the wear deep enough to catch a fingernail on?

#4

Its normal to find oil inside the cover, but It should not pour out of that stator cover hole. The engine may have been overfilled.

#5

If you have access to a Honda shop manual, on page 7-5 it shows the tensioner. As the cam chain wears and becomes slack, the tensioner attempts to take up the slack by the spring pulling wedge "A" deeper into the unit. Wedge "B" locks "A" in place and prevents it from being able to loosen off on its own. Wedge "A" has to be released and pulled out/up (reset) when a new chain is installed.

Wedge "A" is pulled up and a pin inserted into it to hold it up while installing the chain and cam sprocket. Then the pin is removed and the tensioner finds its own equilibrium with that of the chain.

I don't know if you could even install a new chain of the proper length with the tensioner wedge all the way down. It would be trying to pull slack out of a new chain that doesn't have any and seems like it would make it very hard to install the cam sprocket.

 

regarding #3, from the picture the far right rocker looks pretty thin, but honestly i dont remember how it actually looked when we took it off, i wasnt paying attention because we were mostly focused on the chain. i played around a little with the rocker arms and tappets and they all seemed fine to me but then again im no mechanic so we thought we'd post this pic. we'll look again next time we take it off.

 

regarding #5, so you are saying that this tensioner isn't really automatic as you have to pull up wedge A then release it to properly reset it. we tried hard to do that. we grabbed on to it with some pliers and tried to pull up as much as we could with wedge B pressed down but we couldnt get it high enough to access the pin hole. it was a real workout.

 

 

Is there any pitting in the cam on the shinny lobes or are they perfectly polished?  Things look pretty clean in there.

 

The chain looks wrong like you said.

 

no pitting as far as i remember, they were pretty smooth.

 

i thought the chain looked suspicious but im still not completely convinced it's wrong. i dont think i would have even noticed if we didnt take it apart specifically to inspect the chain.

 

im hoping someone else can chime in who knows these parts intimately to either confirm our suspicions or assure us that it's normal.

 

 

thank you both

Edited by md30

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The cam chain and cam gear are not meshing correctly.  When you get the correct cam chain on, there will be NO gap under the chain - it will fit tightly on the cam gear.  It should fit so tight that if you try and lift the chain off the gear you will not to see a gap under it. When the chain tensioner takes up the slack, you won't be able to move the chain any significant amount at all.

 

Remove the chain and replace it with the correct chain.

 

THEN, after assembly and operation of the engine, see if you have any further problems.  I'll bet you wont....

 

:ride:

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one more question regarding this issue:

 

If you get a new cam chain and run it on a bad tensioner which causes clanking noises, will that immediately destroy the new chain, or does the chain only go bad with time due to stretching?

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