250r bottom end rebuild

[carothers]

I have a complete (in a couple of buckets) bottom end for a 85 or 86 250r.
I want to rebuild it for fun and also to get more power out of my trike. Is there a complete kit that I can purchase that includes everything that I will need besides the crank and rod? Also is there a hi temp clear coat I can apply to the cases so that when I polish them I dont need to do it over and over?

[jenndnn3]

I too am doing my extra bottom end. I have heard to stay away from the bearing kits on ebay and stick with stock honda. Someone else also told me it is better to use cr500 bearing on the crank rather then 250.

If we like the way this bottom end performs, I am suppossed to repeat the process.

I going with the 4mil crank and a different tranny.

[3wheelergod]

Jenn is right about the bearing kits! Garbage!:doh: You might as well put a cr500 crank in it and port the cases if you have them apart. IT WILL RIP. Extra stroke and they are a little tougher! You could even use a honda pilot 400cc jug on the top. 430cc with the 500 crank. Awesome!

Dont know about the gloss on the cases. It is a fun winter project to keep them shiny!

[YAMAHONDAMAN]

I too am doing my extra bottom end. I have heard to stay away from the bearing kits on ebay and stick with stock honda. Someone else also told me it is better to use cr500 bearing on the crank rather then 250.

If we like the way this bottom end performs, I am suppossed to repeat the process.

I going with the 4mil crank and a different tranny.
the part no. for the 500 is the same for the 85-89 TRX-ATC's for the Main Brg. ..
any bearing place sell's them for like 16 bux each . # 63/28C3 .. :)
there's NO WAY a CR500 Crank will go into a ATC Motor and with a 4 Mill you need to cut 2mm out of the head or run a spacer place under the cyl .. i personally think "or know" that with the ATC Piston,long rod and spacer plate is FASTER than them 4 mill set ups.. just my 2 cents and.................. on the cases .....
use the smallest glass bead's you can get and clear coat will hold up... even on a polished motor

[carothers]

If I do the long rod w/ spacer plate will I need to change my porting? Or will the spacer compensate for the longer connecting rod? I have never heard of porting the cases, what is involved?

[YAMAHONDAMAN]

YES .... the spacer plate puts the porting the same and as far as Case Porting .... theres some stuff you can do simple ... drum sand the big round area and remove ALL Casting in that area ... theres a dropped spot just below the sleeve ... trim it down ... champer the Sharp edge just above the Main Brg. with a 1/8" Radius... "funnel" the Main Brg. oil feeder holes a little bit ... i wish i had some pics ... in two weeks i will have pics .. i fixen to do a LONG Rod Motor .. i will show you....:thumbsup:

[jenndnn3]

I didnt Say use a cr500 crank, I said use the bearings...but didnt know the trx were the same as cr500 (bearings)
Dont know the performance difference myself between the 2 cranks so this all is good info yamahondaman, look forward to your write-up.

We are not sure at this moment which way for spacer or cut.

[3wheelergod]

the part no. for the 500 is the same for the 85-89 TRX-ATC's for the Main Brg. ..
any bearing place sell's them for like 16 bux each . # 63/28C3 .. :)
there's NO WAY a CR500 Crank will go into a ATC Motor and with a 4 Mill you need to cut 2mm out of the head or run a spacer place under the cyl .. i personally think "or know" that with the ATC Piston,long rod and spacer plate is FASTER than them 4 mill set ups.. just my 2 cents and.................. on the cases .....
use the smallest glass bead's you can get and clear coat will hold up... even on a polished motor


Yes, you can put a cr 500 crank in a 250r bottom end. I requires alot of work on the cases and, they do get very thin but IT WILL WORK! The 4 mil requires a little work too and can really rip when built right. :thumbsup: Trust me! If your getting beat by stock stroke trikes do some more work!:doh: They dont build the 4mils for nothing!:doh: I guess we build crazier motors here!

[likestrikes]

CR500 bearing has one more ball than the 250.

[YAMAHONDAMAN]

They dont build the 4mils for nothing!:doh: I guess we build crazier motors here!
i'd like to see some of "those" Crazy Motors in 300' one day with my old little 250 :oldman: