Low compression 3 1/2

[BumbleBee]

Bumblebee - Good call, not had a look at the valve seats so might be worth a look - I'll see if the adjustments I have made has doen anything first.

Thanks again.

If it is still the same after the adjustments, my experience over a lot of miles has been each time the compression has slowly got worse on the various 3½s I've maintained over the years it has only about 1 time in 10 been the rings. Usually its the valve seats needing lapping. One time I didn't have time to do them before a big ride to Italy and on the way back through France it burned out a valve, the valve was not sealing it was leaking hot gasses between the valve and the seat. So kind of inevitable and my own fault for ignoring low compression.

[George 350]

Andy,
To save you "reinventing the wheel", do you get along to any of your areas section meetings? It could well be that a fellow member might feel inclined to a/offer to assist and b/ might already have the "strong washer" you will need and be willing to loan it.
The washer needs to fit onto the crank pulley where the light spring and belt guide go on, secured with the same circlip.
If the 'washer' isn't a very close fit onto the pulley, or solid enough, it will most likely wreck the circlip, so be careful.
Good luck
George

[Andy_C]

Bumblebee - thanks again, sounds like it might be worth popping the heads off and taking a look, as you say not much effort involved.

George - not yet been to any club meets.

Do you have the dimensions of a suitable "strong" washer, I have a tin in the garage with many assorted washers in it, some pretty thick, and some pretty large, if I have something near enough I can stick it in the lathe and machine as necessary.

[Steve Brown]

Make it in the lathe then! The dimensions are on here somewhere and I think even the books show what you need. It does need to be strong so make it as thick as will fit out of some decent material. It will be dead obvious when you see it, and the choosing of the correct internal spline will also be clear from the pics in the manuals. You can download the blue book and I think there used to be dimensions and pics of all the special tools you might need, on here. I can't be bothered to look though.

[BumbleBee]

Bumblebee - thanks again, sounds like it might be worth popping the heads off and taking a look, as you say not much effort involved.

The heads come off easy, each basically a pushrod single. I'm almost embarrassed to point it out, but when taking the heads off don't forget there's an M6 screw down the pushrod tunnel that needs undoing

[mad muller]

Back street test, have you removed the plugs and kicked the bike over with your thumb over the plug hole it should be obvious if compression is low , should be able to feel the cylinder pressure I could be way off the mark here but have you checked the clutch isn't slipping when you kick the bike over , only one cylinder at a time can be on a compression stroke so in affect your only kicking a 175 cc over , mine is easy to kick over it's not a stand on the pedal job to make it spin , if it runs OK and it sounds OK it can't be far off ,

[George 350]

I think you would need to be a contortionist with very long thumbs to be able to do that on a Morini!

[70sbikes]

Here's the "washer" I got from Ralph Restorations (which seems to have disappeared off the internet).

When you go through the pulley removal procedure, install a new circlip beforehand, it's amazing the difference that will make!

[Andy_C]

Thanks, really approeciate the dimensions and the tip about the circlip.

Looks like a job for the lathe.

Thanks again.

[mad muller]

Yea your right george they are sunk in the depths a bit , it's been at least five years since the plugs were out , but still running sweet , you get the idea, the sentiment is well placed unlike my long plug spanner. Tuto gas . Muller .

[simonnorthroad]

Use a blowtorch on that bottom pulley to get it REALLY smoking hot, then as thick a washer as you can get on there behind the circlip and a 3 legged puller. The heat finally helped shift the last one I tried after Id dished a thick washer trying to shift it.

It may have been loose and the play taken up with Loctite Bearing Fit, which really gums them in place...

[George 350]

Andy,
Before you actually attack the pulley, it might just happen to be correctly fitted. There isn't usually a need to remove it in normal service.
Even if you can't see the woodruff key itself , it is inline with the one for the flywheel location so use that to determine if it is correct.
The manual describes exactly how to determine which keyslot should be used, so with the front cylinder at tdc, you should see the key inline with the 'dot' on the crankcase. If the correct slot is also in line with the dot, then you don't need to remove it! If the pulley is the original factory fitted one then there should be a punched dot adjacent to the correct slot, and it should also line up with the crankcase dot.
Just might save you a lot of grief getting it off only to find you didn't need to.
Hope you get to the bottom of it,
George

[Andy_C]

Thanks George.

I know that the key in the crank aligns with the dot on the crankcase, but hard to see any other marks on the pulley.

I will pop the flywheel off again over the weekend and take a look.

[BumbleBee]

Thanks George.

I know that the key in the crank aligns with the dot on the crankcase, but hard to see any other marks on the pulley.

I will pop the flywheel off again over the weekend and take a look.

My bottom pulley doesn't have a dot on it, but instead it has a notch "ground out" somewhere around the BACK face of the pulley e.g. the end of the pulley furthest away from you when you are looking at it from the normal end. Its can be hard to spot when the dirt builds up

[Andy_C]

George, Bumblebee

Having looked at the manual, it looks like the alignment I am after is pas per Fig 117/B on page 68, although I did set the valve opening point using the method I outlined in a posting further up.

Having said that I still want to fine this elusive dot on the timing pinion.

I did fire it up briefly after re fitting the timing belt, and it started / ran just as it always did, not chnace to test it out as yet.