View Full Version : MHR Lack of compression

31.03.2013, 08:00 PM
Hi Folks,

New to here and looking for some expert advise please. In June last year i lost my father who had been saving his 1982 MHR for a retirement resreration project. In his memory i have taken on the project and have 350 hrs and countless thousands comitted to it since Sept 2012.
The bike has undergone a nut and bolt refurb, engine down and crank rebuilt by Goden in Kent. Back in 95 my dad re bored the bike and re built the top end and it ran about 1000 miles trouble free before being moth balled. So the barrels are good and the heads were only leak tested when removed to ensure valve seats are good.
Problem i have now is that i seem to have a serious lack of compression - 25psi on friont cyl and 0 on the rear when kicking over cold (has not been started yet).
Given the barrelsd and valve seats are known to be good i am questioning myself on the valve timing howver checjed and re checked this on assembly that all the timing marks were assemblied lined up.

Any ideas folks before i go thru the pain of stripping the engine out again for further investigation? Any additioinal guidance on timing up the engine apart from making sire that all marks are matched at once?

Some photos attached, i am nearly done and awaiting the Conti's.



31.03.2013, 08:30 PM
any chance the gauges are goosed?
or is the bike no starting and you decided to do a compression check?

31.03.2013, 08:37 PM
No Mark the finger over the plug hole proves low or no compression, also tested the gauge on my LC and getting good pressure there. Not even got as far as tryinbg to start it yet as dont see any point given what i have just found a few days back with the compression. Valve timing is niggling away at me and the manual is vauge. I am used to rebuilding jap engines so this Bevel has been a massive learning curve

Scott 888
31.03.2013, 09:20 PM
Bevel Cam timing this may help.




01.04.2013, 07:55 AM
Hi Dean

I was going to take a wee run to yours yesterday but ended up gardening! :o

There are already a few pics of your build (pinched off Facebook) on here.

Cannae help with the compression.



01.04.2013, 07:56 AM
Could it be something as simple as the rings being stuck in the piston groove due to lying around so long..!

01.04.2013, 09:11 AM
For the valve timing, on the square case engine it should just be case of ensuring that all the dots line up on the camshafts, bevel shafts top and bottom and the intermediate pinions to the crankshaft. When the rear cylinder is at TDC at the start of the firing stroke with both valves closed the horizontal should be halfway down the inlet stroke with the valve fully open (the opposite of the belt engines since the bevels run backwards).
With cylinder pressures as low as that it sounds like the valves aren't closing properly, at least on the rear. Even with no piston rings there would be some sort of pressure generated.You should check the opening and closing valve clearances to make sure that they are closing properly as it is possible to have them incorrectly shimmed such that a valve is held open.

01.04.2013, 09:12 AM
valve clearance first thing that comes to mind.

01.04.2013, 03:38 PM
do you have pistons inside the barrels , just a thought :)

01.04.2013, 06:56 PM

Thanks for all the help here, i have been at it tonight and have established that when the rear cylinder is at TDC regardless of what stroke i never get to a situation when both valves are closed, either one closed and one open of the other way around.
Next step to remove the genertor rotor and expose all the timing marks again to see if i can see why this may be (still 99% sure all the dots align). I read somewhere that if you mix cams from anoteher model then the timing marks dont tie in - could thius maybe what i have here and need to time up the manual way and ignore the marks?

I wish i had recived the new cyl head nuts before the engine went in and would have cought this on the bench :(



01.04.2013, 07:57 PM
Update - I hang my head in shame as it appears that the 1% doubt that i had the timing wrong proved to be the case!! No idea how i managed this after the fear i had in checking and double checking at the time. Now have 160PSI compression on both cylinders and having to jump on the kickstart like i recall back in 1995 :)

Thanks folks

PS Lindsay still pop roond on Thusday if you are free and i will put the kettle on.


01.04.2013, 09:46 PM
Glad you got it sorted Dean - it looks fantastic. I'm sure your Dad would have been proud.

As Lindsay says we've seen a few shots of the build so would be nice to see her on the road when you get there.



01.04.2013, 10:22 PM
Glad to see you're getting there. Spoke to Lindsay tonight about some possibilities but sounds like you've got it sorted now. Well done. Hope to see this bike out and about when you get it finished. Good luck.

02.04.2013, 12:00 PM
Cheers Kenny, Derek, hope to get it to one of the Scottish meetings this year. Where on the site are the photos saved, i had a rake around but new to here so guess i am missing them.

02.04.2013, 09:10 PM
Dean it's under Classic Ducati on the SDC part of the forum under Santas NCR - one of the usual convoluted threads!

There's a couple of shots of my MHR rebuild there too under "meantime not unajacent to a wheelie bin"

Snappy titles... !

03.04.2013, 06:21 AM
Ahh i see now Kenny, good to see your hard at it with yours also, hopfully catch up this year at one of the meetings.


Scott 888
03.04.2013, 05:45 PM
Had the Black and Gold SS out the garage around lunchtime today ready for its test this afternoon the lure and sound fae they Conti"s was too much.

One Scaffy wagon abandoned in the street :eek:.


02.12.2013, 10:51 AM
Deans MHR will be featured in January 'Practical Sportsbikes' on sale December 14th

Scott 888
17.12.2013, 02:45 PM
Deans MHR will be featured in January 'Practical Sportsbikes' on sale December 14th

Just read Dean's MHR restoration story in this months mag a credit to you and your suppliers.