Posts
284
Joined
11/22/2019
Location
Lodi, CA
US
Edited Date/Time
5/26/2022 6:52pm
I bought this used CR250R 1986 a while back. I am the third or fourth owner.
Started rebuilding it.
There are 2 different part numbers for the cylinder head bolts ( studs ) on the microfiche.
The older ones ( 90016-KS7-000 BOLT, STUD (6X20) )are not available anymore
I ordered the available ones available ( 90011-HA2-000 BOLT, SPECIAL STUD )
well, looks like previous/previous owner installed a big bore sleeve.
I cannot install the studs since they have a 12mm flange interfering with the thick sleeve.
I was about to look for a counter bore to clear the flanges.. but then thought about taking a magnet to check..
the big bore sleeve is magnetic.
I was under the impression that sleeves were aluminum with Nikasil starting in 1986 on CRs.
Assuming cylinder being aluminum, and sleeve too, I thought it would be safe to drill/counter bore the sleeve to place the new studs.
But since the magnet stick to it... if this sleeve is steel, could a counter bore operation be an issue? see pics
I am hesitant to counterbore these. I also have no experience with aftermarket/unknown sleeves. Would this sleeve still have nikasil despite being magnetic? Should I treat it as a cast iron sleeve like 1985 CRs?
Tried sourcing the older style studs. No such luck so far.
What do you think?
Started rebuilding it.
There are 2 different part numbers for the cylinder head bolts ( studs ) on the microfiche.
The older ones ( 90016-KS7-000 BOLT, STUD (6X20) )are not available anymore
I ordered the available ones available ( 90011-HA2-000 BOLT, SPECIAL STUD )
well, looks like previous/previous owner installed a big bore sleeve.
I cannot install the studs since they have a 12mm flange interfering with the thick sleeve.
I was about to look for a counter bore to clear the flanges.. but then thought about taking a magnet to check..
the big bore sleeve is magnetic.
I was under the impression that sleeves were aluminum with Nikasil starting in 1986 on CRs.
Assuming cylinder being aluminum, and sleeve too, I thought it would be safe to drill/counter bore the sleeve to place the new studs.
But since the magnet stick to it... if this sleeve is steel, could a counter bore operation be an issue? see pics
I am hesitant to counterbore these. I also have no experience with aftermarket/unknown sleeves. Would this sleeve still have nikasil despite being magnetic? Should I treat it as a cast iron sleeve like 1985 CRs?
Tried sourcing the older style studs. No such luck so far.
What do you think?
I’m interested as well, as I was getting ready to order studs for the two of my cylinders I’ll use at first. Mine are stock nikasil though.
I got a set of the newer style studs lathed for free by a local machinist.
It's not ideal, I think the newer style studs locate the head on the cylinder better... but being lazy for now.. this is an interim solution to ride the bike.
Long term plans, was thinking of sourcing an original jug, resleeve or replate in oem 250cc. Expensive but then I could source known pistons and rings.
Buuuuut I am also suspecting the power valves MIGHT have been trimmed to clear the 300cc big bore. Sourcing these is another can of worms.
So far, it runs... it holds coolant, does not boil. Starts first kick.
Shocking! it rides like a big bore/ KTM 300 minus the heavier flywheel and the 6 speed gearbox. It likes to be lugged everywhere. Maybe it's the rider getting older than the bike.
A stark contrast with my 93' CR250.
The Shop
Cross check from the other manufacturers
If they show as being long cut to length
Life is good.
Post a reply to: Help needed on 1986 CR250 Head Studs replacement