Not again!!

B-Stone,
Do you live in Edmonton by chance?
Kber45

I live just outside of it. Spoke with John and Ross today about what they think the problem is.

snakehips said:

As for the rear chain being loose, I would ask the people that serviced it if they adjusted the primary chain. If the answer is yes they most likely did it wrong. The manual is clear on how to do it correctly unfortunately it doesn't stress the importance of the correct sequence of adjustment. Basically the adjuster must be adjusted by pushing the gearbox forward towards the engine and not the other way by pulling the gearbox backward otherwise all the freeplay between the bolt and the casing etc will be on the wrong side and it doesn't matter how tight you do that top gearbox bolt up as soon as power is applied the tug of war that exists between the primary chain and the rear chain on the gearbox the rear chain will always win and pull the gearbox backwards taking up the slack in the bolt/casing and making the rear chain slack and making the primary chain like a bow string. This beside damaging the sleeve gear etc will cause you gear selection problems aswell, quick check remove the primary inspection plug and put your finger in and see how tight the primary chain is.
I have found the best way to adjust the primary is to temp overtighten the rear chain slightly or put your foot on it to preload the gearbox backwards to take up the slack while adjusting the adjuster in the forward direction loosening the rear chain as you go and when that is all done and tightened up set the rear chain slack correctly.
Best

Click to expand...

Looked at the primary chain and gearbox tonight and it seemed locked in tighter thah hell. Thought I may as well adjust it while I am down there. In section C41 of the shop manual, it indicates

Now slacken off the rear nut and carefully tighten the forward nut until there is total up and down movement of 3/8 in. (9.5 mm).

This probably sounds idiotic but does this imply that the chain should only be able to be depressed or raised 3/16" or do they mean 3/8" up and 3/8" down? The 3/8" total seems to imply 3/16" up and 3/16" down but damn that seems pretty tight when I set it up like that.

Thanks for understanding if this sounds completely daft but just want to confirm. If it is only 3/16" in either direction then I think I can rule out the gearbox shifting as a reason for the slack drive chain as it was pretty damn close to that before I slackened it off. I also have tightened up the three bolts for the hub/brake drum assembly and this did not magically sort the slack-ass chain.

What the hell else could it be?? Is it possible that the chain just got wickedly stretched after about 50 miles total driving? Maybe I need to take the chain off and measure it?

Thanks again

3/8" TOTAL is correct but find the tight spot first and adjust at this point. You will likely have more at the 'loose' point since chain will wear unevenly.
Use 'Snakehips' method for pushing the box forward. Then adjust the rear on the wheels, preferably with someone on the bike, again after finding the tight spot first (on the centre stand) to 3/4" total play. If the play increases after a run you either have a rubbish chain, no lube on it or sleeve gear bushes on their way out. Check this by hand tensioning the rear chain and watching for excessive movement of the clutch and primary chain. It will change a little since the mainshaft is not that rigid anyway but it shouldn't be moving too much.
Finally make sure those gearbox bolts are done up tight and any backlash in the adjusters will have the primary tighten up and the rear loosen of course. Good luck.

I reckon theres been a problem with the whole primary. It ran with almost no oil for 50 miles? Thats going to root the chain. Did anyone previously remove and refit the the whole primary side, i.e. clutch out, alternator off etc? If so, if the inner case has not be shimmed square that needs to be looked at. Distrorted cases will lose oil. The primary chain has to run in alignment with the engine drive sprocket, otherwise the problem is going to repeat itself, chain stress and excessive wear.

I seriously recommend you pull the whole primary, clean eveything, examine the clutch basket and plate splines. If they wear and dig in they create difficult shiting and may grab or slip. NOTE - some aftermarket plates have wrong spline profiles! Get genuine or guaranteed quality plates. A Commando clutch should be smooth, dependable and allow a seamless gear shift. Fit the inner case with a new crankcase gasket and the relevant shims on the centre bolt to align with the case joint on the crankcase. Fit a new primary chain and re-align and re-tension the gearbox. Grease the rubber band seal before fitting up the outer case.

Inside the gearbox outercover is the shift quardrant movement is controlled by a forked spring. That spring sets the quality of the shift with positive engagement. WIth the shift lever attached, move the lever down 2,3,4th and up 4,3,2,N,1 and obsever the arc of the quadrant enagement. The spring forks just contact the shifter equally on both sides. Too much on one side biases the shifter and changing up or down is going to be compromised. My way of adjusting the shift is to tweak the spring fork at the point of contact on the shifter with pointy nose pliers. Carefully bend it so it just touches the shifter and both forks are equal. Check the arc movement of engagment. If all seems good, just refit the outer cover dry and rotate the back wheel whilst shfiting through the gears by hand. If you get positive selection of all gears up and down, remove the cover, fit gasket and bolt up the case. Use a good quality 80-90W gear oil.

The above was recently carried out on a '72 Combat and resolved slipping and shifting problems, hope it helps.

Mick

Tightened hub bolts.

Re-set primary and rear chain tensions.

After many kicks got the bike running and it was not happy. Wicked clanky noise from the jugs as near as I could tell in the approx 5 seconds I had it going.

Pulled the head off and valves, push-rods, pistons all seem ok.

The left con rod has a couple of tiny cracks staring where the top arch connects to the crank. It is also covered in brown (I assume burnt oil)

I figure I will likely rip the motor out and see what else lurks within but I am still confused as to what the noise is all about. Definetely was no loud clanking when I was kicking it over unsuccesfully. The shop put Boyers on it and I am wondering if the timimg could be completely out of whack/the Boyers cooked again????

So confused....

did you say your con rod has cracks in it ?

Cracks in the rods!!!!! You need to replace them. Old rods do have brown staining due to overheated oil, often from overheated big ends. I recently took my cyls off for painting and the 20,000 mile 'New in 2003' rods were totally clean, no discolouration at all.
What are the rod bearings (big ends) like? Any up down play? Take a look at the crank end play (though this shouldn't clank even if it is over spec). Is there any crank radial play? Alternator rotor and drive sprocket tight?
Some close-ups on those rods would be helpful.

Wow,

What a dismal story. If you were close by I'd just invite you to come over and we'd go through the thing.

The left con rod has a couple of tiny cracks staring where the top arch connects to the crank. It is also covered in brown (I assume burnt oil)

Click to expand...

The brown means it got plenty hot! Being the left rod is typical of oil starvation. Pull the crank and dissassemble it and clean all oil passages. Check the oil pump. Make certain you have not reversed the feed and scavenge hoses to the oil tank. Check crank journal for scarring and have it ground if necessary. (Don't forget the radius!). I have seen this type of failure more than once and each time found evidence of RTV silicone beads on the inside of the crankcase joints and later inside the crankshaft.

The indicataons are your crankshaft was starved for oil which affects the rod furthest from the oil pump (left) worse than the one on the right, leading to failure. Check the right rod journal as well and replace the rod bearing there as well as a new rod and bearing on the left.

You need to find the cause of the failure before you button the motor up with new pieces or you will likely destroy those as well.

Yep,
I worry that he has toasted a bearing. At least there is no hole in the case.

Here is a of pic I took of the left con rod

That sure does look like an oil event Ron. I hope for the best, I have seen a crank come out of one of those looking good. As for the rod only a careful check will tell the story.
You sure have to find the reason.

Being not to bright, what should I be looking for/checking once I get the case split?

The first thing is before you split the case. Be sure you have the oil feed on the right pipe from the oil tank. Check that the lines are clear and if you have a filter it is hooked up right.

B-Stone said:

Here is a of pic I took of the left con rod

Click to expand...

Hi I guess pull the motor all the way down as others have said looks like an oil starvation problem IMHO i would not want to run the engine in case of a severe event like a snapped rod and holed case..good luck any probs with rebuild the forum is the best place to ask

Well here are the pics of the crank and the cases. As you can see, left con rod is burnt. Hard to make out but there are cracks in the con rod where they meet the crank. Plenty of play in the left con rod and suspect the bearing is completely disintegarted.

Barnk bearing appear in good health. Will take it in to check the overall crank condition this week. Hopefully it is not too badly scored.

Thought I would throw pics of to show progress etc.

Cheers

B-Stone