Finished rebuilding my top end! Now what...

[poorman9]

Over the past few days I completely reassembled the top end of my engine, honed the cylinders, installed new rings, gaskets, valve stem seals, new cam chain tensioner, cleaned everything out, etc... (read about it here if you like.)

I've never even seen this engine in one piece let alone heard it run. I've a bit nervous, this being my first build, but everything went together pretty easy, now I'd like to see how I did. I've put my carbs back on with new pod filters, an got my new exhaust attached, so the engine is sitting dry on my workbench.

Questions:

I've got a compression tester, can I/should I do a test without any electrical hooked up, without any oil in the moto?

Would it be okay to try and start the engine before it's in the frame? If so, any precautions?

I've heard I need to check and recheck the head bolts for torque specs once I get the thing started up and I should kick it over several times to getting the oil pumping before I start it, any other advice?

 

[hotdog]

Before you do a comp test, squirt a little oil in the barrels, comp test should be done with W.O.T. as well if you have fitted the carbs.

Yes you can do a comp test with no electrics, if you have fitted the electrics make sure you earth out your plugs.

Vid of one of Punkskalars rephased 277" motors in his stand.

Cheers.

 

[retiredgentleman]

There should be no need to do a compression test. Hey poorman9, you just re-built the top end, so have confidence in your own work. You can do a compression test after the engine has been running.

I think its a good idea to do a rough carb sync with the carbs on the bench................just use a strip of paper under the butterflys to get equal drag. That will have the sync very close. Use a manometer when the engine is running.

Put it back in the frame. Add new oil. Adjust the valve clearances. Adjust for rough or static timing. Pump the kickstarter about 20 times to prime the oil system................then start it up.

Re-check head torques the next day after running. Re-check again after 100 miles................again at 200 miles.

Once running, use a timing light.

Have fun riding

 

[poorman9]

Thanks for the list!

And you know, you're right, I should have confidence in my own work.

 

[poorman9]

For anybody interested in a conclusion to this story, last night after a couple hours of electrical problems I started my motor up for the first time. It felt good knowing that just a few days ago I had the engine in about 50 pieces!

 

[retiredgentleman]

poorman9;

Well done..................take it out on the road for some short runs and let us know how it handles.

 

[KentMoney]

I don't wanna hijack your thread, but I am at a very similar point on my 1981 xs650 rebuild.


I personally split the crankcase and I am adding a new 5th gear along with a crankshaft rephase. when I am finished with this and it comes time to put the crankcase halves back together, do I have to take special care to ensure that the shifting mechanism is seated properly on the transmission gears? Or will it just 'fall into place' on its own? It seems to me that the shifting mechanism's 'claws' need to be seated on certain points of the transmission gears, how do I ensure that they are in the right place?


Thanks everyone!

 

[azman857]

Build your bottom end with the motor upside down. Once all bottom end is done and cam chain in, turn the engine over and assemble the top end. Thats the easiest way.

 

[KentMoney]

and so this way I am able to put the transmission gears directly onto the shifting claws to ensure they are seated properly?

 

[azman857]

Yes. I don't know of any other way to do it.

 

[KentMoney]

awesome, sounds like a good solution to me! Thanks for the reply.