Topic: 750 k6 camchain and head gasket questions

[jmuthaf]

My 77' cb750k6 has about 34,000 now on the clock and is now becoming louder and leakier (again). 

Last summer I pulled the motor, and replaced the stock head gasket , due to it leaking oil on the cyl. #1 side. The head gasket kit i bought was an after market set, with all new o rings, I had the cylinder head plained down to make sure it was flat and used a copper coat sealant on the head gasket. I followed the directions to a T, (except) Re torquing the head after 2000 miles. I didnt want to pull the engine again as its my understanding i cannot pull the valve cover off in the frame, though i have not tried. Now after about 4000 miles on the bike after the head gasket replacement, shes pushing oil out both sides 1 and 4.

The noise i speak of, Is timing chain noise. Yes i know these bikes are prone to it. But its becoming louder than I want. I've pulled the tensioner, making sure it's absolutly free, and lubricated. I've tryed both method's of adjusting the timing chain, while its running, and 15 degrees past TDC on #1. Neither really quiet it down. The noise is loudest when cold, and takes a good 4-5 min of idle before it quiets down some. After the bike is up to temp, it dosnt sound horrible, but still has more noise than i would like. When i had the head off last summer, The tensioner block looked ok, no significant wear so i did not replace it.

So this winter, i'm going to tear the motor back out, and replace the head gasket with a Nos honda gasket, and o rings. I want to replace the timing chain and anything i can to quiet it up. My questions are, Is there a non endless timing chain i can get, where i dont have to pull the crank to replace it? What else should i look at or replace to keep the noise down? As for keeping the Cylinder head sealed up, what should i be looking for or doing to keep it dry? Thanks for any help in advance!  -Josh

here is a pic of the ol' gal..

[Old Scrambler]

Its probably not your head gasket.........more likely the oil is leaking near or around the exhaust spigots and is pushed to the sides of the head/barrels by the wind.  One strong recommendation is to get a HONDA oil seal and gasket kit and when you have the head open, check the pads/o-rings under the camshaft/rocker bridges.

The cam chain noise is a mystery........they are usually louder after running a while.  If you shaved too much material fromt the head it will cause improper alignment/timing. With the motor set at 15-degrees past tdc on #1, try placing a very slight amount of pressure on the adjuster pin and tighten in place.  Endless chain equals pulling the crank.  My original chain has less side play than a DID replacement after 70k.  Then check your timing.  If the timing is off it will cause the chain to be streesed at a slightly different interval.........especially if timing and carbs are spot on for 2 cylinders and somewhat off for the others.  Even one carb can be out of tune and cause stress.  Also, when you motor is warmed up and idling, while listening to the motor, pull in the clutch and note the sound difference.  If this is very noticable, your primaries may be stretched and/or your carbs are not balanced.

[JohnG]

ditto the last post...  it's probably not the headgasket.  Just went through this problem myself.

The "pucks" under the cam tower need alot of good sealant around them.  Also if you look at how the cam towers and so on are fastened down, some of those bolts are "open to the atmosphere"  at the bottom and thus need sealant put on them.

Basically lay the head and block out on the workbench, get a cup of coffee and a notebook and ask yourself "what is any possible way oil could get out of the engine?"  .  Once you have a sense of each place, then decide how to attack it.   I spent $3 each for 6 of the new pucks and am putting sealant on them as I believe they are my biggest problem.

Cam chain: do you know the tensioner is working properly??  Can you check this while it is assembled and on the bench before you tear it down?  I used to see the plunger get stuck in the adjuster from time to time, for example.

[jmuthaf]

Yeah, i didnt figure it was actually the head gasket leaking but an o ring around one of the cylinder studs. i never thought about those pucks, but this time when everything goes back together i'm going to use some high temp sealant on anything rubber and OEM Honda parts.

The carbs are synced as close as a 4 vacuum gauge will sync them. As far as the tensioner working properly, the roller wheels and everything looked in good shape when i had it apart last summer, and the plunger unit is very free.

I thought i remember reading that some one makes a timing chain that has a rivited master link? is this true? or does any one know where to find such a thing?

[jmuthaf]

breakable timing chain? anyone??

[Spanner 1]

I think its your primary chain, especially if noisiest when cold.....can drop the pan and check tensioner from below.....

[MCRider]

breakable timing chain? anyone??

You can break the stock chain and use a rivet master link from a CB450 to put it back together. You'd need the rivet peening tool.

Many will cringe at this suggestion, but I see it as a viable option, though I have never done it. The CB450 chain could not be endless by design. They are the same size, 750 and 450. THe 450 racers rev very high, and have a more circuitous run than the 750.  Never heard of one breaking. And if it did would it be at the master or somewhere else?

I might not do it on a built engine as the master link won't match the HD cam chains. But a stocker no problem.

Then again, its not that hard to go ahead and split the cases and put an endless HD chain in.

[MCRider]

I think its your primary chain, especially if noisiest when cold.....can drop the pan and check tensioner from below.....

YOu can measure the wear from below, but you can't do anything about it without splitting the cases.