Topic: cb400 cam chain adjuster thread gone. Suggestions please!!

[horror]

Hi there

    I tried adjusting the cam chain following the haynes manual. It says to use the engine running method.
I realised that the thread in the engine case has gone, so the chain adjuster just rotates in the hole and does nothing.

does anybody with experience of this have advice on how to fix? this bike was supposed to be a quick cheap fixer upper to
ride for the summer.
Would it be possible to heicoil the thing without removing the engine?
Maybe I could tap it out to a larger thread and put a bolt in there.

[horror]

See this image, I am uncertain as to how the mechanism works at this time.
Can it be tensioned without the locking bolt and lock nut?
Is it possible to adjust with the blanking bolt bit?

[hoodellyhoo]

The mechanism works by having the part labeled "adjuster" pushes on one end of the "arm" (also called a horseshoe). The pivoting arm them pushes on the "slipper" which bends and applies pressure on the cam chain.

To answer your question, no, you can't adjust it with the blanking bolt, only with the locking bolt (which presses against the adjuster and keeps it from moving). I have no personal experience, but apparently the only way to do it is to split the cases. Otherwise I don't think there is a way to keep metal shavings out of your motor.

[camelman]

DON'T split the cases.  I just went through this with mine.  I didn't want to separate the cases to drill it out for tapping a larger bolt or heli-coil.  I found that the hole left after the thread stripped out was exactly the size needed to tap the closest standard thread pitch (1/4 by 24).  You could use 1/4 by 20 also.
The best part is that you don't have to drill, so you don't have to take the bottom half of the case off.  Be careful with the tap though. It will only go part way in, so you'll need to "cut" the rest of the threads by working a bolt in there.  Don't worry, it works fine on this soft aluminum.

I spoke with a local shop, and the guy there said he does away with the dual pitch bolt.  He just steps up to the next larger size bolt with a single thread.  It is easier, and it adds more strength to the hole to reduce future strips.

Camelman

[horror]

Good I was hoping I could do something like this, I thought I could take out the blanking bolt and put a longer one in to push on the adjuster but I suppose the mechanism wouldnt lock.
I also whondered weather I could do the tap out method as You described, and take the thread off the end of the bolt I use, leaving a smooth bit on the end that goes into the adjuster.

Thanks cheers.

[Bodi]

In theory you could use the blanking bolt like you suggest. You will need a section of treaded rod or a long metric bolt that you've filed a fair bit of the tip down to fit into the smallish hole past the case threads. A locking nut and flat washer will also be needed.
You would have to be VERY gentle with this method, you could easily over tighten the cam chain which would potentially cause it to break and would definitely cause accelerated wear on the cam bearing journals (already a weak point with the steel cam running in plain aluminum alloy journals) tension blade, and slipper blade. Access to this bolt is difficult with the engine running since the red-hot headers are uncomfortably close. You will need to adjust it while running, tightening it until the cam chain just goes quiet, then snugging up the locking nut to make sure the tension stays put.

[camelman]

Bodi,

You nailed it with your statement "tighten it until the cam chain just goes quiet".  I think it is very important to also stress that "snugging" the lock nut in place should be done gently.  It doesn't need to be cranked down.  I think my tensioner tore out the thread because the locknut was tightened too much in the past... probably by me too.

Camelman

[fasturd]

A long time ago I read a thread regarding taking a stock bolt grinding a taper on the end and using it and a lock nut as the new adjuster. I did it and made one for my friends 400 and my S/Os 400 it works great. I also used an allen socket bolt as it is much easier to adjust than a standard hex nut in that particular location. As stated earlier be careful adjusting tension and then locking the bolt in place. Nothing needs the be strongarmed into place.
Good luck.

[horror]

I went to the local tools shop and got a 10 mm bolt for te rear mudgaurd. I noticed that it was the same thread so I tried it in the
adjuster hole. For some reason the new one would go in tight, but the old tensioner bolt and locknut will not tighten. I suppose the new thread is sharper or something.
Here is what I did to fix it (hopefully)
I put the screwdriver in the hole as described and it went quiet, then I used the new bolt, with an old horn mount rubber to seal it.
I wonder weather it will hold, I had to do it up quite tight (hoping it would not slip) to get it to stay adjusted, as soon as I loosten it the chain
goes noisy again.

[camelman]

Let us know how long it stays tight.  You have to adjust it pretty often anyway, so you'll be tightening it back down often.  Also, it wouldn't hurt to clean that engine!  ;-)

Camelman

[horror]

Yea the bike needs cosmetic work, I'll do that last tho ha ha.
I may still try doing it with the threaded bit in the blank off bolt hole, seems like that is les likely to slip that way.

[Industrial Rat400f Killer]

There's some good info about the 400's right here on this site.

Here's the general list of stuff
http://www.sohc4.net/index.php?q=node/185

Here's a link specific to the cam chain adjuster

http://www.sohc4.net/index.php?q=node/194

[schwebel]

I used a different fix when my bolt snapped. I placed shims between the dampener and dampener holder. I cut up an old feeler gauge. Problem is that it is trial and error with how many/ and thickness of the shims. It works really well, it's just not as easy as turning a bolt.

[DarcyCB400F]

Camelman... can you tell me how long the 1/4" bolt is?
I tried adjusting mine today and found it that it's stripped too... 
I am thinking that I should drop the oil out of it afterwards to avoid any aluminum shavings getting into a journel or somewhere I really don't want it!

What stops the oil from leaking now that I have lost my o ring set up?

I am also glad that I don't need to split the cases! Phew! 

[-CB-Jamie-]

The PO of my bike must have stripped the threads in the crankcase too on my bike, but he came up with a handy enough solution to it. He had a big SS nut with a 6mm thread welded onto to the crankcase and then threaded a 6mm SS bolt through this with a locking nut on it with a washer. Whoever done the welding on this thing was really tidy as well. Now there should never be a problem with stripping threads again hopefully. Also when I got this bike it had been sitting for at least five years and the bolt loosened with minimal effort. It's tidy enough looking as well.

look closely in this pic and you can see it.

[bollingball]

When ever using a tap put some grease in the flutes to help capture shaving take it out every couple of turns clean re-grease no shaving in motor

[BCX6880]

... He had a big SS nut with a 6mm thread welded onto to the crankcase and then threaded a 6mm SS bolt through this with a locking nut on it with a washer. ...

Can you weld SS to aluminium? How? Closer pics, please. Thanks

[-CB-Jamie-]

... He had a big SS nut with a 6mm thread welded onto to the crankcase and then threaded a 6mm SS bolt through this with a locking nut on it with a washer. ...

Can you weld SS to aluminium? How? Closer pics, please. Thanks

Well I'm pretty sure the nut is SS anyway. The bolt definitely is and I'm 99% sure the nut is. I don't know the first thing about welding so I wouldn't know how to do it. It's definitely welded though. The engine is back in the bike so it's a bit hard to get closer pics but here's what I got.

[specweld]

must be another material, stainless does not weld to aluminium.

[BCX6880]

... It's definitely welded though...

Simple, effective ... brilliant. Great tip. Could be JB Welded?. Thanks

[-CB-Jamie-]

Well as I said I'm almost certain it's stainless but however it's done it works perfect anyway

[DarcyCB400F]

I removed the top bolt, removed the cam chain tensioner bolt, started the bike, gently pushed down with an allen wrench through the top bolt hole... nothing moved... nothing! I tried a gentle push through the tensioner bolt hole... again nothing moved. Gave the bottom hole a long very skinny screw driver and with the engine running, and someone pushing through the top hole, gently tapped the screw driver... still nothing.
In the end, I could not get any movement what so ever in the adjuster to quiet the chain.

Becasue the bike has been sitting and not running for 10 years, could it be that the tensioner is stuck?

What do I do now??

[-CB-Jamie-]

I had to push down through the top bolt hole to tension my cam chain too and it didn't really take too much pressure, it was just kinda ackward trying to hold the screwdriver I used down and retighten the bolt to hold it as I did it on my own. Does sound like your tensioner is stuck Darcy but maybe someone with more experience might chime in.

[DarcyCB400F]

Thanks Jamie. I was wondering how much pressure was needed while pushing down.
I sure could use some advice here as I am stumped as to why I can't get any "play" in the adjuster...

I shared a Guiness or two with you last week!! How was your St Patricks Day Celbration?

[-CB-Jamie-]

No bother. I don't know can't remember Paddy's Day nah only joking I was a good boy, only 6 or 7 pints + some vodkas. It was pretty good here, hit the town about 2pm after the parade and stayed out til about 10 or 11, pubs were jointed though as they usually are for Paddy's Day here. Is there much interest for it in Canada?