GRiSO running on one cylinder?

There should be drilled holes in the flywheel that correspond to compression TDC for each cylinder; although normal italian rules apply on whether they actually are there in all cases. Ideally (I did it) you would use the screwdriver down plughole plus the alignment of the cam sprocket plus the flywheel marks to be 100% of TDC - I've even put white marks on my flywheel to help centre it.....

Screwdriver down plughole is OK although there is a bit of potential error at TDC due to piston direction switch where flywheel moves but piston doesn't travel up or down much - just across, so a mark out on flywheel accurate to couple mm is a big help bearing in mind we are trying to avoid an error of 1 tooth at the cam sprocket. Klaas - not sure what you mean as the mark is either in middle of window at TDC or it's not - whatever stroke the engine !

The cam sprocket needs to align with the opening per my photo & normally you 'park it at that point' but since that has slipped you now want ideally more than just one indication that all the other bits are at the right point - without TDC mark on flywheel it is purely screwdriver down plughole I think - before you set the sprocket aligned to the bolt holes !

The TDC mark on the flywheel isn't always there. Mine doesn't have it.

.

I'll buy you one

TBH mine didn't either on RHS cylinder but by lining up the cam sprocket plus fiddling with screwdriver through plughole; I marked up my own for future reference

paulbrice wrote:

There should be drilled holes in the flywheel that correspond to compression TDC for each cylinder.

That's incorrect Paul, there can be a hole for TDC, but not for compression TDC.

paulbrice wrote:

mind we are trying to avoid an error of 1 tooth at the cam sprocket. Klaas - not sure what you mean as the mark is either in middle of window at TDC or it's not - whatever stroke the engine !

We are looking for the COMPRESSION TDC, right now we don't know whitch of the 2 that is, the sprocket and chain are still connected so we are not looking at a tooth wrong, there is no such thing.

If I was the owner of this bike I would wait till Pete Roper is back from hollidays

Sorry Klaas, and you are 100% correct on what we are trying to do here given the sprocket slipped with the teeth still correct - I was generalising about the use of the TDC mark on flywheel as a useful guide under normal conditions (off on a tangent as usual)...

...and agree to get proper guidance !

paulbrice wrote:

I always thought you were supposed to check the valve clearances with ALL the valves closed ie at top of compression stoke. Not sure what difference it makes but it looks like you are doing the exhaust side with the inlet valves wide open ??  Or am I missing something ?

Yep. I just had a look at the videos.

You have to check both inlet and exhaust clearances at TDC of the compression stroke. Go back and do them properly.

Sorry Beetle but that isn't the problem now, look at the picture he posted with the guidance pin sticking out.

I have no timing marks on the flywheel so I will indeed wait for proper guidance.

klaas123 wrote:

Sorry Beetle but that isn't the problem now, look at the picture he posted with the guidance pin sticking out.

It still will be a problem when the cam/chain/pin problem is fixed.

.

beetle wrote:

klaas123 wrote:

Sorry Beetle but that isn't the problem now, look at the picture he posted with the guidance pin sticking out.

It still will be a problem when the cam/chain/pin problem is fixed.

.

It isn't an issue.  I made an error when I checked the exhaust valves a week ago.  I know top dead center on the compression stroke is where the engine needs to be, I've done it four or five other times on this bike and many dozens on my BMW's, Suzuki's and Triumphs (which all conviniently have timing marks on the flywheel).  I made a mistake and that mistake occurred because I was in a tired rush and the cam is out of phase on one cylinder.  I should not have any free play in the exhaust valves when the engine is at TDC on the exhaust stroke which means i shouldn't have been able to even slide the feeler in at that point in the engines cycle.  By showing the feeler could fit in on the wrong stroke I was illustrating the engine was indeed out of phase.    

So that being said once its all timed properly, setting the proper valve clearances at the proper point in the engines cycle (TDC compression stroke) will not be an issue.

OK, good.

If the pin has come out of the cam sprocket due to the flinger being out of position, the question is, how did it happen?

Look, now you've discovered the cam pin has slipped out, (I know this happens but I'm still baffled how anyone with half a brain can think it's a good idea to line ip one of the holes in the flinger plate with the pin?) the chances are the chain hasn't slipped on the sprocket at all. Apart from anything else as long as it's not been disassembled it won't be possible for the chain to jump a tooth, there simply isn't enough wear in the pins to allow it!

What you're going to have to do is set it up at TDC on that side using the straw trick, (There are no timing marks on the 8V flywheel.)and un tension the chain on the cylinder. Then undo the sprocket retainer bolt and when it's loose wriggle the cam pin out. Then pull the bolt out completely along with the flinger ring and cable tie the sprocket to the side of the head. It should still be timed right as the chain won't of jumped a tooth.

Now, with care, re-insert the cam pin and tap it home and then turn the cam and crank until you can align the sprocket and slip it onto the cam boss and pin. Having not lost the sprocket timing in relation to the crank you should now find that when you return the piston to TDC the alignment of both the pin and the sprocket will be correct in the 'Six o'clock' position.

You can now put the flinger plate back on and tighten the retainer bolt MAKING SURE THE HOLES IN THE PLATE DO NOT ALIGN WITH THE PIN!

Once that is done you can check and set your valve clearances BUT....... Look very carefully at the adjusters and observe how much the actual threaded parts stand proud of the top of the locking nuts. If there is a substantial difference in the *Height* they protrude between the inlet and exhaust valves then whatever one has the 'Shorter' adjusters I'm afraid those valves are bent because they have clouted the piston when the cam timing was lost. Don't even bother trying to start the engine, pull the head, replace the valves, start again. You can't save a bent valve.

Pete

beetle wrote:

OK, good.

If the pin has come out of the cam sprocket due to the flinger being out of position, the question is, how did it happen?

I've never seen one come from the factory misaligned like that so one can only surmise that at some point, (During rollerisation maybe? I can't remember what year this machine is?) the flinger ring has been removed and then not reinstalled with any care for the alignment of the hole.

What is really annoying is that there is no bloody reason I can fathom for those poxy holes to be there in the first place!

Pete

I thought this was a factory roller?

I loose track.....

I bought the bike new in 2012 and it has a roller in it. It wasn't converted since I've owned it unless it was done before I purchased it.

So the "straw trick" is good enough in determining TDC? I was expecting something more precise and far more difficult to do.

As Pete says there isn't a mark on flywheel for both cylinders (seems variable if there are any); and since your sprocket has slipped you already lost another key alignment point. So screwdriver and care to be in the 'middle of the top' OK.

I've always worked on cars with lots of alignment marks & even camshaft locking tools to get it right so maybe my fault to cause the concern - sorry for that. Having said that the 'float' around TDC on pistons can lead to an error close to one tooth (approx 14 degrees of the GRiSO cam sprocket) if you go at it without some care - see below although I know it's a different config/dimension set. Error may explain why there have been a few bikes left 1 tooth out on rebuild.

This is close, but not very accurate (Screwdriver). There will be a small range of motion of the crankshaft near TDC that will produce very little motion of the piston. Crankshaft "throw" (eccentric distance) for the connecting rod journal in the MG (Austin) B-series engine is 1.75 inches (half of 3.5" stroke). Height of the piston is a function of cosine of the angle from TDC.  Cos(0)=1.000  Cos(5)=0.996   Change of height of the piston at 5 degrees will be (1.000-0.996)x1.75 = 0.007 inches. Therefore a change of 10 degrees at the crankshaft (+/-5d from TDC) only moves the piston 0.007", which is very hard to see or to feel with a probe. So sight or feel is not going to give you exact TDC position

Before anyone shoots, I am aware cam turns at half rate to crank so the degrees will be 50% less out!

So the only way to accurately get TDC is with a dial indicator, degree wheel and the head off. Cam in block would be really nice right about now.

To be honest that would be overkill by a square mile - I just think it needs care. The plug hole is pretty square over piston so if you eye level the straw/screwdriver whilst gently turning crank you'll be able to judge the mid tip point pretty well (would be close to a dial indicator down the plughole).

Either way a 1 tooth off is the least of the worries at this point given the valves might have took a bump

Read the first pages of this rollerzation how-to by Pete Roper to learn a bit more about this matter.

readme

Don't worry aboout tooths off, it ain't going to happen as long as the sprocket stays connected to the chain.