Transplant for my CB250RS

[ktm84mxc]

After trawling the Honda bike specs this is what I've found
1985-87 CBX250rs DOHC 72-61 bore & stroke RFVC head
1984-85 XR250 SOHC 75-56.5 bore-stroke RFVC head
1986-87 XR250 SOHC 73-59.5 bore-stroke RFVC head
1986-87 XL250 SOHC 74-58.8 bore-stroke RFVC head
1997 CBX250 SOHC 75-56.5 bore-stroke RFVC head
I have limited my search to models with the RFVC head design, it appears Honda just kept tinkering with the models as the Twin carb was a failure.

[nzspokes]

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After trawling the Honda bike specs this is what I've found
1985-87 CBX250rs DOHC 72-61 bore & stroke RFVC head
1984-85 XR250 SOHC 75-56.5 bore-stroke RFVC head
1986-87 XR250 SOHC 73-59.5 bore-stroke RFVC head
1986-87 XL250 SOHC 74-58.8 bore-stroke RFVC head
1997 CBX250 SOHC 75-56.5 bore-stroke RFVC head
I have limited my search to models with the RFVC head design, it appears Honda just kept tinkering with the models as the Twin carb was a failure.

the CBX motor that carried on in the GB250 seems to only have been dropped when they came out with the I4.

The problem with the dirt bike motors was not the carbs but the heads cracked when the bikes overheated.

[actungbaby]

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Depends on how far you want to go??

I have a GB 500 motor which I am fitting into a CB250rs which will take some mods

It lines up with the rear mounts ok, but needs spacers made up for the rear and will need to make new plates for the front and top mounts once thats all sorted,I need to shift the tank mounts on the frame to lift the tank of the motor and change the rear tank mount and widen the frame,so I can fitcarb in, then build and fit an oil tank for the GB motor....

Another option I did consider and fitted rather well,was keeping the 250RS bottom end changing the top gearbox casing for a 500 to fit the 500 barrel and head,but will need things beefed up.....


I haven't updated the blog on here for a while as I have been rebuilding a bike for the Mrs

I was thinking about this for my lemon vt 250 know its black in colour the lemon is the engine inbetween
As cant seem to get replacment vt 250 engine what about single in there . i was thinking it whould be okay
get engine mounts right but what about the engine sproket right angle to the rear does this matter ?

I love to get bike working as looks nice and and running gear look great any thoughts

I imagine where not trying fool anyone but if didnt notice i guess save on getting it certified
What are the rules i thought u changed the engine it cost alot to have it checked over ?
If not cool i might give this serous thought as its nice light bike and seem have good blance feel not even ridden it pushed it lots hehe
Well home like 7 kms

A cm 200 engine whould be nice or 400 gb engine oh course i got find one those that works okay

[actungbaby]

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Anything can be made to fit if you have the desire & patience.
The biggest I thought you could take a 250 RFVC {CBX,XR} single to was 280cc as the engines are over square, try fitting the Hot up parts like cam, piston, exhaust etc from White bros, XR only's, Yoshi.
Those little XR's can be made to scream if you chuck enough money at them. A CBX is just a retuned XR for the street.

yes i have to agree you can get hot up bits for them get head shaved up the compression a bit bigger carb or flatslide
carb with right jet sizes you probley want get that done for you.

Mind you just getting engine top end cleaned up valves machined not laped done right and new set rings
And or rebore or hone and bike go alot better even carb tuned air fliter just geting serviced make world diffrence
in right hands ie mechanic not me
cause half time you pull bike to bits and run out money and stay that way least you got working bike keep that way
get old wreak work on that insteed i got vt 250 hehe
one in the hand is better than 2 in the bush not thats not right...

[dogsnbikes]

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I was thinking about this for my lemon vt 250 know its black in colour the lemon is the engine inbetween
As cant seem to get replacment vt 250 engine what about single in there . i was thinking it whould be okay
get engine mounts right but what about the engine sproket right angle to the rear does this matter ?

I love to get bike working as looks nice and and running gear look great any thoughts

I imagine where not trying fool anyone but if didnt notice i guess save on getting it certified
What are the rules i thought u changed the engine it cost alot to have it checked over ?
If not cool i might give this serous thought as its nice light bike and seem have good blance feel not even ridden it pushed it lots hehe
Well home like 7 kms

A cm 200 engine whould be nice or 400 gb engine oh course i got find one those that works okay

Really depends how far you want too go,as long as everything is alined properly (use a laser level) to line things up if your doing it yourself...what ever engine you use the engine mounts will be your biggest issue,if they are too wide?spacers can be made up providing the rear engine holes line up with the mounting points on the frame,making adapter plates for the front is another option,once you start cutting up the frame you will need it certifried....

I am using a certifried engineer as I will be cutting the backbone of the frame,

[Sable]

The whole bike is trash, throw it away.