Repairing crankcases and counter bore machining

[greg brillus]

Hi there again, Well the modified 4 speed has most likely had the secondary dog teeth ground off the gears to enable quicker shifts, causes a bit of extra backlash in the drive system. I have ridden several road going bikes with their gears moded in this way...doesn't seem to make too much difference to me...As for the oil pump, if it's a road bike....do away with the two start pump drive worm and go back to a single start variety. The extra oil delivery for a road engine is unnecessary, remembering that the engine has a roller bearing crank that doesn't need huge amounts of oil pumped into it, only the cams and followers need all they can get, which can be delt with by carefully setting up the components within the timing chest....to be continued....cheers...Greg.

 

[Brian Thompson]

My mate is going to be disappointed with your oil pump suggestion. He loves that oil pump scroll. Got it off kel Carruther's a million years ago. I'll pass on your thought's. Thank you again. I hope you don't get tired of my question's before I get it apart.
brt650

 

[bmetcalf]

The two start pump requires a splash shield in the filler neck to keep the squirts in the tank. This has been discussed a bit on these pages by Tom Gaynor and others.

 

[Ken Tidswell]

The 2 start oil pump will need a small modification to the oil tank return in top of the UFM . A plate is needed to deflect the oil down into the tank. Otherwise you will get oil coming out around the cap and the neck of the tank. You should find an aluminiun welder with a good reputation for using the best procedure for welding the case, and then someone who can machine the resulting welds. Then get it on a the slab and check for distortion. Ken

 

[timetraveller]

Stick with the two start worm. What the other chaps have not mentioned is that it is not only a two start worm that will have been installed but should also have been a plunger with inclined teeth, as opposed to the orignal which has teeth parallel to the plunger axis. Think about it chaps, you should never fit just a two start worm as it will not mesh correctly with the orginal plunger. The extra oil might not be necessary but it does not do any harm and every engine I have built for the last 40+ years has had a two start pump fitted. Also the extra backlash on the gears will hardly be noticable so save time and money and use what is there if they are in good condition.

 

[vibrac]

Yes dont worry about double back lash and in all the years of racing I never used a 2 start pump but then (as I often end my notes I use castrol R

 

[Brian Thompson]

Hello,
I have ordered the 5 speed on Tuesday. Hopefully it's on it's way. I should get the engine soon. I think I'll bring all 3 engines home and see what I have to work with.Thank you again for your support.
Brian

 

[johnmead]

I just installed a pair of Terry Prince's 600cc topends. His recommendation is to bore the cases so you have .002 clearance which is a slip fit.

John Mead

 

[Brian Thompson]

Thank you for that John,
We are going to see him at the end of October. Hopefully we'll come away with everything we need. I should have the engine next week.
Cheers
Brian