bulto58 Posted January 9, 2014 Report Share Posted January 9, 2014 Hi All, Looks like i'll be splitting the engine on a 250 Mar I've just acquired. It only selects 1st and 2nd ,and I have seen a posting from scotty in 2007, which had a good reply from woody. There was no outcome posted , so wondered if anyone as come across this since. Also does the engine drop out the frame easy, looks quite tight . Quote Link to comment Share on other sites More sharing options...
woody Posted January 10, 2014 Report Share Posted January 10, 2014 I don't remember the post you mention but with an Ossa, the problem could be anything, shimming of the shafts, shimming of the selector drum, worn pins on the selector drum, damaged selector fork(s)... I have heard of people managing to remove the engine from the frame without taking off the cylinder, but I've never managed it. I take the cylinder off and them remove the engine. To take the cylinder off, remove the two front engine bolts, remove the rear upper bolt and them push the front of the engine down slightly, pivoting it on the lower rear bolt. You can now get the head and cylinder off. With the engine in its normal position there isn't enough room to get the cylinder off, it hits the top tube. Or you can tell us how to remove it as a complete unit if you manage it... Steve Sell is down your way, he has a lot of knowledge of Ossas, he'll be at the Telford show trading as Marlimar. Quote Link to comment Share on other sites More sharing options...
trialsrfun Posted January 10, 2014 Report Share Posted January 10, 2014 (edited) I bought my OSSA MAR/TR77 which I am currently restoring with the engine already out of the frame, a friend has been a great help with the engine rebuild & shimming set up. Thank you, I am sure you will read this. Steve Sell MarliMar OSSA stocks all the shims in varying thicknesses to enable crank & gearshafts to be set correctly. Just started a dry build to get everything sorted out before having the frame powder coated and found that the engine does not fit back in the frame at all easily when assembled, the head steady brackets on the frame top tube were catching the fins on the cylinder head. Removed the cylinder head & it fitted easily. Just blank off the two ports & bore first. We used industrial blue paper towel (well worth getting a big roll to keep by your workbench) One thing to be aware of with the OSSA engine, I did not know this, is the cush drive on the crankshaft. It is secured with a taper & impossible to remove without the special puller. I have heard of heat & bars being used but it always ruins the spring & or breaks the flange off the part that goes onto the crank taper. There is a OSSA handbook on the web http://www.custgp.co...l2/Ossa 250.pdf fill the printer with ink & go for it you will need it. The special tool is shown in there & could probably be made on a lathe. The parts pages were also really useful we had these printed A3 http://www.custgp.co... 1972 parts.pdf Edited January 10, 2014 by trialsrfun Quote Link to comment Share on other sites More sharing options...
bisby Posted January 10, 2014 Report Share Posted January 10, 2014 Trialsrfun, thanks for the link on the manual (now saved to my comp, my clyimer manual is now very well used) and ossa grippers are very almost the same inside the cases. Bulto58, the only thing that i can add to Woody and Trialsrfun is i find it easier to loosen or take off the flywheel and cush drive with the engine still in the frame. if its your first time inside the engine a camera is handy for a photo record. good luck Steve. Quote Link to comment Share on other sites More sharing options...
bulto58 Posted January 10, 2014 Author Report Share Posted January 10, 2014 Thank's all for the info. I could see removing the engine in one might be a problem, so now i'll have a good start removing the cylinder first. woody you said about Steve Sell down my way, I've seen is name mentioned a few times, does anyone know is actual location , I intend to go to Telford show and try and get info too. Thanks for the link, and like you say bisby, I'll tackle the flywheel and cush with the engine in. Thanks all. Quote Link to comment Share on other sites More sharing options...
trialsrfun Posted January 12, 2014 Report Share Posted January 12, 2014 PM on its way to you re; Steve Sell. I do not wish to post his contact details on an open forum but he is in your area. Quote Link to comment Share on other sites More sharing options...
basketcase Posted January 19, 2014 Report Share Posted January 19, 2014 Hi, I managed to get the engine out in one, but I`m not looking forward to getting it back in now that my frame is freshly powdercoated!! I`ve covered the down tubes and top tube in pipe lagging and hoping that that is enough to stop the scratches! I don`t fancy taking the top end off as the engine ran lovely before I took the bike apart, just giving it all a coat of paint to freshen it up. Cheers, basketcase. Quote Link to comment Share on other sites More sharing options...
trialsrfun Posted January 20, 2014 Report Share Posted January 20, 2014 Hi, I managed to get the engine out in one, but I`m not looking forward to getting it back in now that my frame is freshly powdercoated!! I`ve covered the down tubes and top tube in pipe lagging and hoping that that is enough to stop the scratches! I don`t fancy taking the top end off as the engine ran lovely before I took the bike apart, just giving it all a coat of paint to freshen it up. Cheers, basketcase. Please let us know how it goes but I think you will have to remove the cylinder head to refit the engine. Quote Link to comment Share on other sites More sharing options...
bulto58 Posted January 20, 2014 Author Report Share Posted January 20, 2014 Hi all, Just removed clutch side case tonight, and give it a bit of looking at, I will get back to all, and probably be asking a few questions too, may take some time. Cheer's Quote Link to comment Share on other sites More sharing options...
twinshock giles Posted January 29, 2014 Report Share Posted January 29, 2014 Hi All, Looks like i'll be splitting the engine on a 250 Mar I've just acquired. It only selects 1st and 2nd ,and I have seen a posting from scotty in 2007, which had a good reply from woody. There was no outcome posted , so wondered if anyone as come across this since. Also does the engine drop out the frame easy, looks quite tight . As has been said before they are mega tight to get in/ out, I think i've managed it in the past but I know it was a huge struggle. Onto the gearbox, i've twice had gearbox problems with Ossa's which isn't bad to be honest for the amount of engines i've built up from misc bits Once was the detent plunger on a 250 MAR that had worn and had a large ridge on it - that bike would only select 3rd 4th 5th, took a while to find it but changing the plunger fixed the problem. The other was my 350 Gripper which wouldn't select 1st and was general bad at changing down the box - the fork that turns the end of the selector barrel was badly worn on one leg only - i think someone must have been in the habit of constantly taping it down to make sure it was in 1st. Never had much of a problem getting Ossa flywheels and cush drives off, as Steve says it easier with the engine solidly mounted - remember to check the thread direction of the flywheel nut BEFORE trying to remove it early bikes are the opposite thread. Giles Quote Link to comment Share on other sites More sharing options...
bulto58 Posted January 30, 2014 Author Report Share Posted January 30, 2014 Hi all, Yes engines out,ended up pulling head and barrel, cush removed.My order from Inmotion ( gasket set / crank seals ) arrived today so hope to split the engine this weekend. Thanks for info twinshock giles, I too wonderd about the detent, I've got hold of some gearbox spares, so be back with news soon as. Thanks Quote Link to comment Share on other sites More sharing options...
bulto58 Posted February 9, 2014 Author Report Share Posted February 9, 2014 Hi all, problem solved, replaced the selector return spring and selector drum.Seemed the selector pawl was not returning back for the next gear change, but getting stuck on the drum pin. Thank's for the Info. Quote Link to comment Share on other sites More sharing options...
trialsrfun Posted February 9, 2014 Report Share Posted February 9, 2014 Hi all, problem solved, replaced the selector return spring and selector drum.Seemed the selector pawl was not returning back for the next gear change, but getting stuck on the drum pin. Thank's for the Info. Pleased to learn you are up & running. Fitting an engine makes you think they built the frame around it they are such a close fit. I am taking my frame to be powder coated so will have the fitting issues soon! Quote Link to comment Share on other sites More sharing options...
ian e Posted February 24, 2014 Report Share Posted February 24, 2014 Just to add, I met up with Steve Sell at Telford on Friday eve to drop off my Gripper 350 engine which has failed mains. Good guy, knows his stuff, I've owned this bike since it was a year old ( ex Pete Salt works) so after 33 years I want it done correctly! Want it back for Aqueduct's Foel 2-day later in the year. Thanks to others who have given me email advice too ( Steve Bisby etc) 1 Quote Link to comment Share on other sites More sharing options...
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