Pulling the Head

If you need technical information or help with your bevel drive Ducati single cylinder engine - post your FAQs, comments & questions here.
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Mat
Cucciolo - the Lil Pup
Posts: 15
Joined: Wed Nov 27, 2013 6:36 am

Pulling the Head

Post by Mat » Fri Dec 06, 2013 2:38 pm

Looking for any advice before I pull the head on my 1964 250 Monza. I got this bike not long ago and knew it would need some work. Compression was low about 40psi maybe. I adjusted the valve clearance and did a simple leak down test and find leakage back thru the intake valve. Looking thru the spark plug hole cylinder looks a bit funky, kind of like it was honed but not really a crosshatch pattern but hard to tell thru hole. I noticed one of the head bolts looked to be missing its washer under the bolt head and putting a wrench on the bolts this one seemed a bit loose. I guess I should retorque the bolts just to be sure that they do hold up to torque but it looks like the head will have to come off anyhow. I have a Clymer book on the singles. It looks like I should loosen the cam bolt(left hand thread) before pulling so I won't need the cam holder tool. Any other advice. I am new to Ducati but not to bikes and engines having worked with British, Japanese and German. Thanks, Mat.

GeoffW
Mariana
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Re: Pulling the Head

Post by GeoffW » Sat Dec 07, 2013 2:52 am

It's over 30 years since I overhauled a bevel single motor, but my memory tells me you don't need to touch the cam nut just to get the head off but you can be cunning and loosen that nut before you get the head off as a cheat. Then you just set the motor to TDC on compression stroke, undo the head nuts and pull the bastard off then, real easy. Is my memory failing me guys? Oh, and pull off the carbie and exhaust, pull the spark plug out and undo the oil lines…i.e. do the bleeding obvious before you undo the head nuts. I love these little motors, just a work of art!

ducadini
750 Sport [BEVEL]
Posts: 246
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Location: Antwerpen

Re: Pulling the Head

Post by ducadini » Sat Dec 07, 2013 10:04 am

The part about TDC and compression is ok, better still is to take the top-bevel and rightside cover off and turn the engine over 'till the markings on the inside of the bevels align (that should be TDC and compression).
Take care not to drop the shims that are on the ingnition shaft.
Then the oldhamcoupling is inline with the engine.
This can take a few turns : the ratio crank-cam is 2-1 but the ratio crank-shaft is , eh "something" and the ratio shaft-cam is also "something else".

ciao
joseph
Nego i ricordi peggiori
Richiamo i migliori pensieri

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Robin172
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Re: Pulling the Head

Post by Robin172 » Sat Dec 07, 2013 10:24 am

Unless you plan on removing the camshaft there is no need to loosen the cam bolt before removing the head. Just turn the engine over to line up the dots on the cam bevel and the bevel shaft gears (behind the top bevel cover). Remove the head bolts and pull the head off.

If you turn the engine over to inspect the bore, make sure that you remember which way you turned it so the you can reverse direction and get it back to the same position at TDC otherwise you will have to pull the lower timing case off and line up the bottom bevel and timing gears. In other words, if you turn the engine clockwise to get the piston at BDC you must turn it anti-clockwise to get it back to TDC, do not carry on clockwise to get back to TDC, this is all to do with the ratios on the timing gears.

If necessary you can remove the valves and springs without touching the cam, however should you need to do any work on the valve seats, other than lapping the valve in, you will need to remove the cam, in which case I suggest putting the head back on the engine and tightening down to do that.

Before you put the head back on the engine, either to loosen the cam bolt or to finish the build, make sure the dots on the cam bevel and bevel shaft gears are lined up again.

Mat
Cucciolo - the Lil Pup
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Joined: Wed Nov 27, 2013 6:36 am

Re: Pulling the Head

Post by Mat » Tue Dec 10, 2013 12:38 pm

Thanks all for your input. I will make sure to align up the bevel gear markings before pulling head. I have some more mundane stuff to get out of the way before I start this project but thought I would ask some questions first. I will go ahead and pull the engine from the frame so I can work on it on the bench as soon as I get this other stuff done. These little engines do look like a work of art.

Mat
Cucciolo - the Lil Pup
Posts: 15
Joined: Wed Nov 27, 2013 6:36 am

Re: Pulling the Head (am I missing something?)

Post by Mat » Sat Dec 21, 2013 2:57 pm

Well, I pulled the side cover, top bevel cover and lined up the dots. I loosened and removed the 4 head bolts. Carb and exhaust are off of course and I even pulled the oil lines( not sure why that needed to be done). Head is loose but doesn't want to come off. Looks to me to be held up by bevel shaft cover tube. I thought the upper part of the tube would slide off the lower part which is attached to crankcase. There is some movement between the two, a millimeter or two so I don't think it is frozen. If I remove the two bolts holding the lower part of the tube to the crankcase the head comes up farther but is lifting up the lower bevel. Am I missing something here or is something not right? Don't want to force it.

ducadini
750 Sport [BEVEL]
Posts: 246
Joined: Sat Jul 31, 2004 9:54 am
Location: Antwerpen

Re: Pulling the Head

Post by ducadini » Wed Dec 25, 2013 3:27 am

there's an o-ring fitted in the lower part, so it could be a tight fit or sealed with sticky stuff.
Fasten the allen bolts of the lower part and gently pull.
Be very carefull using screwdrivers and other tools inserted between head and cilinder, You don't want to break any fins.

joseph
Nego i ricordi peggiori
Richiamo i migliori pensieri

Mat
Cucciolo - the Lil Pup
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Re: Pulling the Head

Post by Mat » Wed Dec 25, 2013 5:20 am

Thanks for the input Joe, I figured that there would be an o-ring sealing the shaft tube, I can see the tube move maybe one millimeter or so at it's separation point. I can see that the head is loose from the barrel and also that the barrel is loose so it is not stuck there. I am going to have to get a second pair of hands to hold the engine while I wiggle and pull at the head. I am kind of wondering if the collar that holds the two pieces of the bevel drive shaft to the head has some damage that will not let the shafts come apart. Hopefully maybe it is just a stuck o-ring.

Mat
Cucciolo - the Lil Pup
Posts: 15
Joined: Wed Nov 27, 2013 6:36 am

Re: Pulling the Head

Post by Mat » Wed Jan 08, 2014 6:14 am

Still no-go on getting this head off. The bevel shaft must be stuck in the collar, I read in the manual where the collars come in slightly tighter internal diameter if there is a problem with wear on the shaft itself. Maybe someone used one of these undersized collars and somehow forced the shaft together into the collar? I tried partially suspending the engine by the head using some rope around the intake and exhaust flanges and up to my shop ceiling so that I could wiggle the head while the weight of the engine pulled down but still can't get it come off. I can see that head is plainly loose from barrel and that barrel is loose from case. I have tried moving the crank back and forth with this tension pulling the head with no luck. I will keep trying but not sure what else to do.

Mat
Cucciolo - the Lil Pup
Posts: 15
Joined: Wed Nov 27, 2013 6:36 am

Re: Pulling the Head

Post by Mat » Tue Jan 21, 2014 3:32 pm

Finally got the head off and it appears it was just that the collar that holds the bevel shaft together was a tight fit. I ended up partially suspending the engine by using some rope attached to the intake and exhaust flanges and up to the ceiling rafters. I threaded a solid bolt into the oil return hole on the bevel tube and tapped this bolt upwards which slowly got the head to come off. Thanks for the input. I have some more questions but I will start a new thread.

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