top end rebuild!

[thejake456]

i was wondering what all i have to do for it. i know when i put it in i have to oil the piston up with the two stroke oil before i put it in and i have to mix it richer while breaking it in. but how rich do i mix it????

just to clear things up with my friends, you should always break in a bike after a rebuild, RIGHT????

 

[jasonent0613]

when i rebuilt my cr250 last all i did was warm it up gently then i let it cool down and then i just rode it normally

 

[helio lucas]

the iron liner cylinders are more sensitive to break in process than the aluminium plated cylinders... so if it´s to break in a iron one just warm up the bike and let it cool... twice... then just be very gentil on the throttle and load the first time you rode it... then for the next times just speed up progressively to normal speed...
for plated cylinders you could cut the run in process in half, but is better to go on the safer side...

just put a little bit more oil in the premix. if you are in 32:1 then could go, say, 30 or 28... but not too much...

 

[rmc_olderthandirt]

just to clear things up with my friends, you should always break in a bike after a rebuild, RIGHT????

It is generally a good idea, but it certainly is not always the case.

For a "shade tree" mechanic a gentle break in period will help correct for a multitude of sins when you assembled the engine. If the rings are little too tight, the cylinder hone a little rough, a bit of dust / dirt left in the bottom end, things not lubricated well enough on assembly, etc. then a gentle break in period will help out.

There are plenty of engines that get put together and put out on the race track with no break in period to speak of.

The bottom line is that a break in period certainly won't hurt and it might help. If you aren't scheduled for a race I would ride it gently for the first hour.

Rod

 

[thejake456]

thank you all for your imput. know what do you guys recomend me using for gear oil???? would just the regular 10w-40 work????

 

[btm1948]

i use 10w 30 non synthetic just strait oil. if you search the threads you will find people who have used alot of different things

 

[thejake456]

well i got it rebuilt but now i am having troubles with it. when i start it it runs fine untill it gets warmed up then it just shuts off and wont start back up untill it cools down. i need help!!!

my one friend suggested that the rings are too tight and when it gets hot they swell up. but that didnt make much sence to me cause i know for a fact that the piston and rings are the same size as before. it didnt do that before the rebuild

 

[_JOE_]

What did you set the ring end gap to?

 

[thejake456]

i dint. i dont know how to do that???

 

[whenfoxforks-ruled]

Before assembly, you check the ring end gap and piston skirt clearance. Also the exhaust bridge, if it has one. Shop manual covers this, and it is cheaper than the parts you will need to fix it again, sorry.

 

[_JOE_]

Before assembly, you check the ring end gap and piston to skirt clearance. Also the exhaust bridge, if it has one. Shop manual covers this, and it is cheaper than the parts you will need to fix it again, sorry.

I think you meant piston to cylinder clearance.

 

[thejake456]

ok well i dont know how to do that so i will leave that to the professionals and take it up to my local bike shop. does anyone have any idea how much it will cost to do that??? they charge 50 bucks an hour for labor.

 

[_JOE_]

Figure at least 2 hours to pull it down and measure it all out. Probly a few more to repair the problem and reassemble.

 

[thejake456]

what!!! i can tear the top end apart and rebuild it in under an hour! i only got 400 bucks to spend so you think it be under that??? it better! lol...

 

[whenfoxforks-ruled]

You must have a tool set, you claim you can did a top end? Take it apart, take the cylinder to your shop and have them measure it, ask if you can watch. Get a price for parts from your dealer, then go get a quote from Service Honda. Before you ask, call them and ask how much.

 

[thejake456]

yes, i have done top end rebuilds before but never did i run into this problem. i measured it and it is the stock 66mm. thats what i took out of the quad and thats what i put back in it.

 

[whenfoxforks-ruled]

A shop manual would be priceless!