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86 CR250 engine swap help

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Hello everyone! It's been a long time since I've posted, but I'm in need of some help and this is the place to go! Basically, last summer I got myself a 1986 Honda CR250. The bike was in pretty rough shape, no oil in the engine, no coolant either, the piston was shattered and cracked and the crank had a ridiculous amount of play, and of course the water pump was severely corroded. But I saw potential in the bike, and I don't have the heart to part it out. The bike has been sitting in boxes for about a year now, my main race bikes have been getting all the attention, but winter is near and I'm sick of having this bike tease me. So I've got a question. Has anyone ever put a newer CR250 engine in one of these frames? I don't expect it to be a direct fit, I understand the motor mounts would likely have to be relocated along with other things, but is it possible? If so what engine would work best? I understand I will have to look out for things such as chain alignment, gas tank clearance, swing arm bolt diameter etc. I'm really hoping this is a plausible option as I can see the practicality of putting a newer engine in it (parts availability) because the amount it would cost to rebuild the 86 engine is crazy. What do you guys think?  I definitely wouldn't do a hack job on it, I have respect for these bike unlike the neglectful owner I got it from. Thanks guys! 

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Hello everyone! It's been a long time since I've posted, but I'm in need of some help and this is the place to go! Basically, last summer I got myself a 1986 Honda CR250. The bike was in pretty rough shape, no oil in the engine, no coolant either, the piston was shattered and cracked and the crank had a ridiculous amount of play, and of course the water pump was severely corroded. But I saw potential in the bike, and I don't have the heart to part it out. The bike has been sitting in boxes for about a year now, my main race bikes have been getting all the attention, but winter is near and I'm sick of having this bike tease me. So I've got a question. Has anyone ever put a newer CR250 engine in one of these frames? I don't expect it to be a direct fit, I understand the motor mounts would likely have to be relocated along with other things, but is it possible? If so what engine would work best? I understand I will have to look out for things such as chain alignment, gas tank clearance, swing arm bolt diameter etc. I'm really hoping this is a plausible option as I can see the practicality of putting a newer engine in it (parts availability) because the amount it would cost to rebuild the 86 engine is crazy. What do you guys think?  I definitely wouldn't do a hack job on it, I have respect for these bike unlike the neglectful owner I got it from. Thanks guys! 

Try an engine out of an '87, '88, '89, '90 may be pushing it. I've got a bike very similar to yours I'm going through right now, an '86 cr250 in a box lol. Parts are out there and pretty easy to find if you want to fix the engine. There really isn't much there, your crank can be rebuilt by Ken O'Connor racing for around $150 I believe. Let's see some pics of it, engines aren't cheap, I've looked lol. They'll run $800+ easily. BTW do you have a shop manual? Those are helpful

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Try an engine out of an '87, '88, '89, '90 may be pushing it. I've got a bike very similar to yours I'm going through right now, an '86 cr250 in a box lol. Parts are out there and pretty easy to find if you want to fix the engine. There really isn't much there, your crank can be rebuilt by Ken O'Connor racing for around $150 I believe. Let's see some pics of it, engines aren't cheap, I've looked lol. They'll run $800+ easily. BTW do you have a shop manual? Those are helpful

Thanks for your reply! There is an 89 running bike up for sale near me-but a big part of me is completely against modifying my frame which i would likely have to do. I would much rather rebuild the engine I currently have, it's just in really bad shape. Here is a list off the top of my head that the engine will need:
-piston
-crankshaft
-cylinder
-reeds
-misc power valve components
-transmission bearings
-main bearings
-clutch basket
-clutch
-power valve/water pump gear
-water pump/clutch cover

The list goes on...I know there are certain components that can be rebuilt such as the cylinder. I'm hoping i can bore the cylinder over to clean up the walls. It's funny you mention the crank. I met a guy at a harescramble I attended earlier this summer and he told me that he was running a hotrods crank meant for a 92-01 CR250 in his 86! So i've planned to put one of those into my bike. If i decide to rebuild the engine instead of putting a later model one in. I don't have a shop manual unfortunately- but I manage, i can see the benefits though. Here she is, Project Margot:
IMG_4541.jpgIMG_4545.jpg
IMG_4550.jpgIMG_4585.jpgIMG_4609.jpg

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I forgot to mention all the JB weld that was holding the bike together. And the spray paint! It pains me to see these beautiful bikes in such a neglected state. I can't wait until the day I have this bike all done!

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I think you(we?) can save this bike. I'm working on one exactly like it and am about to completely rebuild the engine. I've been through the powervalve and it's pretty simple, parts are available on eBay. The crank is the same from '86 all the way to '99 I think, same with pistons, rings, bearings etc

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That water pump housing can be saved, there is a fix on here somewhere, pretty much use epoxy to build it back from corrosion and use waterless coolant

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That water pump housing can be saved, there is a fix on here somewhere, pretty much use epoxy to build it back from corrosion and use waterless coolant

That water pump housing is in rough shape....that wall by the inlet/outlet fittings corroded all the way through...possible to rebuild, but keep an eye out on eBay for one in better shape...does the '89 cover fit the '86? The '89 cover may be aluminum.

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I think you(we?) can save this bike. I'm working on one exactly like it and am about to completely rebuild the engine. I've been through the powervalve and it's pretty simple, parts are available on eBay. The crank is the same from '86 all the way to '99 I think, same with pistons, rings, bearings etc

I'd love to see some pics of yours! You're right about the power valve being simple, it just looks really intimidating lol! I wasn't aware of the part compatibility through 99, that will most certainly help, thanks! As for the waterpump, i had considered repairing it but sofiedog is right. It's really rough, I know the 89 cover will work however it does require some modification and is apparently not a direct fit according to some on the internet. I want to get this thing back together but it will take a long time- I'll likely be doing it in little bits because of money and time. There is a guy that makes replica clutch covers for these bikes, I know i have the website I just forget the name. That may be the route i take
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If you do find the name of the site could you post it please. I may consider that as an option too. Mine looks a little dismal in this picture, this is how I bought it:IMG_0635.jpg

It's all mostly there minus the radiators and a brake hose I think. It's a work in progress

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OP, I know you're all enthused about doing this repair/rebuild but have you REALLY looked at the wisdom of the endeavor?  The financial part of this thing MUST be somewhat of a concern for you ???  You know what I'm getting at. You may end up with $4,000 into a bike (or even more!) when you could have bought an already restored or just a nice untouched bike for less than half the money and have it available to ride immediately.  I really hope you examine this whole thing and make a wise decision.  Not to discourage you...but that thing needs BARRELS of money dumped into it.  Good luck.

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OP, I know you're all enthused about doing this repair/rebuild but have you REALLY looked at the wisdom of the endeavor?  The financial part of this thing MUST be somewhat of a concern for you ???  You know what I'm getting at. You may end up with $4,000 into a bike (or even more!) when you could have bought an already restored or just a nice untouched bike for less than half the money and have it available to ride immediately.  I really hope you examine this whole thing and make a wise decision.  Not to discourage you...but that thing needs BARRELS of money dumped into it.  Good luck.

I appreciate your insight. The money most definitely is a concern but I enjoy doing this. I will spread the cost out over a period of time so it won't be as painful
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motoxvet is right...you should sell it to me...nice bike...looks like everything is there in original condition...definitely, worth restoring...may not be so bad...but, won't be cheap.

It is complete and i've got the ownership too! She's a diamond in the rough....very deep in the rough

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I could be wrong but i believe the 85-89 bottom ends were close to the same. I know for a fact the 85 bottom end would work. The 88 and 89 are not as popular so you may find one a a decent price.  Problem is any used bike will probably need a full rebuild anyways. Ive said this many times before make a complete list of what you need and not just the motor. Its a 30 plus year old bike. How tight is the rest of the bike. Bearings, brakes, suspension including linkage, chain and sprockets,  tires,  rims, carb, and so one. You don't want to invest $1500 in a motor to put it in a pos bike. At some point a bike becomes a money pit. Ive been there, never again.  

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I could be wrong but i believe the 85-89 bottom ends were close to the same. I know for a fact the 85 bottom end would work. The 88 and 89 are not as popular so you may find one a a decent price.  Problem is any used bike will probably need a full rebuild anyways. Ive said this many times before make a complete list of what you need and not just the motor. Its a 30 plus year old bike. How tight is the rest of the bike. Bearings, brakes, suspension including linkage, chain and sprockets,  tires,  rims, carb, and so one. You don't want to invest $1500 in a motor to put it in a pos bike. At some point a bike becomes a money pit. Ive been there, never again.  

I've made the list. The bike needs pretty much everything other than rims and a frame but as i've said this project will be spread out over a period of time. I've had bikes that have been money pits. I Know the 86 had a one off powervalve and therefore a one off cylinder. Did that not effect the cases?

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I've made the list. The bike needs pretty much everything other than rims and a frame but as i've said this project will be spread out over a period of time. I've had bikes that have been money pits. I Know the 86 had a one off powervalve and therefore a one off cylinder. Did that not effect the cases?

You'd think that, but the cylinders can be interchanged with other years because the powervalves from '86 to '90-'91 I think all are activated the same way. There is an arm, kinda looks like a golf club lol, coming out of the bottom end that pushes the rack in the cylinder one way, which in turn spins the shafts attached to the valve linkage in the cylinder, this opens and closes the valves. It's beauty is it's simplicity once you understand it.

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You'd be better off scoring a complete lower unit, As long as everything functions. cases ,trans, clutch, crank, etc.  Then score a couple other major components (jug) as you go.

Edited by 87' CR 5003

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