First Bike/Build

[Drova]

I've always owned a quad and sled and always wanted a dirt bike, but never did own/drive one. Few days ago i came across a 1984 CR 125 in great shape, fresh engine but had a few small problems, so i figured a great project for me! From what i was told the bike was leaking coolant out the over flow and needed new bearings in the back wheel.

After buying the bike i found out some more history on it. The guy who owned the bike before me was driving it with a coolant leak and kept topping it up with water every so often. Anyways after awhile he rebuilt it but was after warping the cylinder head. So he got the head machined and was suppose to be perfect but when he put it back together with all fresh parts the bike spits coolant out of the overflow when you rev it up, so he gave up on the bike for the last 2 years until i bought it.

So far i checked all lines and both rads for blocks, new rad cap, next i hauled off the head to look at the head gasket (which don't look like the right one to me) but i noticed that where he got it planed down its causing the piston just strikes off the head (not enough to do any damage what so ever) :whoa: I am going to bring the cylinder and head to a machine shop to see if it is warped up again and i am thinking on putting a thicker base gasket to raise the cylinder enough so it does not strike off the head, can i do that???

Any help would be greatly appreciated.

 

[Drova]

Can anyone tell me how i can post a picture of the cylinder head gasket so someone can tell me if its the proper one or not

Thanks Again

 

[helio lucas]

send it to my e-mail, i will post it
yes, you can do that... leave a gap between the piston and the head about 1-1.5 mm
good luck :cool:

 

[Drova]

Was talking to a guy last night and he was telling me that if i can't see anything on the head then its the water pump seal, and on the bikes reverse stroke she pressureizes the base and drives the pressure out through the water pump seal. Hopefully thats what it is!

 

[jsantapau]

Was talking to a guy last night and he was telling me that if i can't see anything on the head then its the water pump seal, and on the bikes reverse stroke she pressureizes the base and drives the pressure out through the water pump seal. Hopefully thats what it is!

I wouldn't go with that idea,


you should check the top of the cylinder, along with the head to make sure it is flat, besides the thicker head gasket you can also machine the combustion chamber a bit for more clearance

"but i noticed that where he got it planed down its causing the piston just strikes off the head (not enough to do any damage what so ever) "

be careful of the no damage statement even though the piston isn't broken the stress can and will move right through the bike whether you damaged the piston pin or big end bearings, bent the rod or knocked the crankshaft out of phase

Maybe the bearings are worn already and that is causing the piston to contact the head?

 

[zoommx]

I would agree to look to the head sealing as a cause for the coolant out the overflow. Damage from piston collisions should be easy to detect after removing cylinder.
Also very important on those older CRs is the clutch cover is made from magnesium. Most of the water pump areas are very corroded from regular coolants and water. Often the corrosion gets bad enough the coolant will contaminate transmission oil. Just a known problem with the 82-86 liquid cooled CRs. (81s had aluminum covers!)

 

[Drova]

Well i have the motor stripped down right now so i am gonna go through it with new seals and crap just to be on the safe side. Apparently parts for these bikes are easy to find and i am pretty sure i have a cylinder and head tracked down so i'm gonna replace it with that so i don't have to go fooling with raising the head i have now, gonna bring the new head to a machine shop before i put it together to make sure it aint warped up.

Now i just need to find 2 parts for my clutch, the push rod that goes through the motor and the small lifter the clutch cable attached to.

And as regards to the water pump housing pitting i noticed she is pitted quite a bit.

I wish a 81 cover would fit :< lol

 

[Drova]

Can anyone tell me if the crank case off a 86 is the same as an 84? someone told me it was not but looking online it seems to be the same.

Thanks