NSR motor swap?

[Chrome-CRF]

Does anyone know if a CR85 will bolt into an NSR or are the mounts even close? For what its going to cost me to build up this stock motor I could get a CR85 with a 102 big bore and make double the power. Just curious if any NSR guys have done any 2 stroke swaps with a bigger motor. I can only find YSR swaps.

[PlanetMinis.com]

[reefmuncher]

The mounts are very different at the rear of the engines. The NSR has two at the rear where the CR uses a single one. You can make a bracket to fit the CR engine quite simply with two mounting plates on each side of the engine. That setup will put more vibration into the chassis though but my mate has done it this way.



My MH 80 which is basically a CR on a NSR uses rubber mounts to reduce the vibration. The performance of the CR engine is well above that to the NSR motor!!

[Chrome-CRF]

The mounts are very different at the rear of the engines. The NSR has two at the rear where the CR uses a single one. You can make a bracket to fit the CR engine quite simply with two mounting plates on each side of the engine. That setup will put more vibration into the chassis though but my mate has done it this way.



My MH 80 which is basically a CR on a NSR uses rubber mounts to reduce the vibration. The performance of the CR engine is well above that to the NSR motor!!

Cool, do you have any pics of the setup? I found a few but nothing up close.

[reefmuncher]

I found a picture, but it doesn't give much more info. I know they are aluminum plates which cradle the engine and the templates were made with cardboard. Also one of the rear frame mounts was removed if I remember correctly.



From what I can remember it looked straight forward to do.

[johnson05]

Its been done a few times. There's one for sale on the amra page right now. AMRA Template I saw a different one for sale last fall.

[Chrome-CRF]

Its been done a few times. There's one for sale on the amra page right now. AMRA Template I saw a different one for sale last fall.

Yeah thats where I found the picture of the black one above. Looks like I am going to have to fabricate a bottom cradle to hold the motor.

[Jimmer]

I have done this to my NSR. Personally if it is going to be a race bike I would recommend using solid mounts, just my opinion.

[Chrome-CRF]

Very nice jimmer, where are you located? How do you like the phathead on there?

[reefmuncher]

I have done this to my NSR. Personally if it is going to be a race bike I would recommend using solid mounts, just my opinion.

Yeah interesting you mention that, on the Moriwaki you have to keep the chain tighter than you would normally do so as the engine torque pulls it back and in the first gear you can get chain skip. Also because the gear shift is on a linkage it moves up and down slightly as a result.



Even with the rubber mounting the bike vibrates alot unless you are in the powerband. When you are in the powerband the bike is butter smooth!!

[Jimmer]

Yeah interesting you mention that, on the Moriwaki you have to keep the chain tighter than you would normally do so as the engine torque pulls it back and in the first gear you can get chain skip. Also because the gear shift is on a linkage it moves up and down slightly as a result.



Even with the rubber mounting the bike vibrates alot unless you are in the powerband. When you are in the powerband the bike is butter smooth!!

I actually do not notice much vibration even with the solid mounts. I however have been doing this off and on for awhile as back in 1988 I was one of the first to put a YZ80 engine in a YSR.



Here is a link to my NSR in action at the MSR track near Fort Worth TX. YouTube - racingjimmer's Channel The bike should even be faster now then in the video. I have a race at my local kart track at the end of the month, I will try post a video to youtube the Monday after the race. This thing is stupid fast for a kart track and being I still have the stock front brake set up I have to start slowing down way too soon for the corners. I am about to put a 4 pot Brembo front caliper with a 250mm rotor on it. After that I am going to have David Behrend at Fast bike Industies rework my stock front forks and set me up an Ohlins rear shock for my weight. When those mods are done I should have everything under control.

[Chrome-CRF]

You're the man Jimmer....that bike is fast as hell.

[reefmuncher]

I actually do not notice much vibration even with the solid mounts. I however have been doing this off and on for awhile as back in 1988 I was one of the first to put a YZ80 engine in a YSR.

That vid looked fast for sure!!



Yeah the vibration tended to be highest I guess around 4000rpm or so. When you'd rev it the cowl would shake around that rpm making fittings go slack over time if you didn't keep on them. I lined my cowl with thin 1/4 foam from a furniture store and it was amazing how much quieter the bike was and it also reduced the vibration or at least changed the rpm it occured. I guess the cowl acts like a guitar body and amplifies the sound of the engine and pipe.

[fatcaaat]

Really, what's the bike for? If its for racing, then by all means the swap makes sense. If you are just going to ride it on the street, I really think a large displacement 4-stroke would be better...Not a takegawa or Nice...maybe a 250? Or like a 175cc twin? Now that would be sick.

[Chrome-CRF]

Really, what's the bike for? If its for racing, then by all means the swap makes sense. If you are just going to ride it on the street, I really think a large displacement 4-stroke would be better...Not a takegawa or Nice...maybe a 250? Or like a 175cc twin? Now that would be sick.

Going back to my two stroke roots. I've got plenty of 4 strokers on the road including my ZB50 with a Kitaco 108se, CRF450 supermoto and my old Aprilia RS50 with YZ426 transplant.

[mike515]

For Jimmer or anyone else who's crammed a CR85 motor in an NSR, what do you use for a pipe? Does your pipe allow the full NSR bodywork to fit?

[Chrome-CRF]

For Jimmer or anyone else who's crammed a CR85 motor in an NSR, what do you use for a pipe? Does your pipe allow the full NSR bodywork to fit?

All the conversions I have seen required a custom pipe. The stock bodywork fits if you route the pipe correctly.

[Jimmer]

I had my pipe custom made to my specs and my bike (with fairings). My pipe guy can replicate the pipe for you however there is no guarantee it would fit unless you engine is mounted in the same exact location as mine. Best bet is to find someone local with pipe building skills and take them your bike.



On another note here is a on board video from my bike at my last race in October. I blew the start, and the two guy's in front are on highly tuned KX65's. you might want to fast forward to about the 4 minute mark as I did not edit it as of yet.

[fireman_343]

What the hell has been done to those 65's to get away from ya?? Are they still 65cc's?

Bike sounds like it would smoke a set of rear tires real fast!

[mike515]

Thanks for the info! I hope to do something to one of my NSRs this winter, so I'm looking into all my options. It looks like it runs real good from that video.



If you don't mind me asking, about how much does it cost to have a custom two-stroke pipe like that made?

[Jimmer]

What the hell has been done to those 65's to get away from ya?? Are they still 65cc's?

Bike sounds like it would smoke a set of rear tires real fast!

I believe one of them was a 72cc bike and I think the other is a 65, not sure though. I also think they have a Rekluse clutch in them so they are always in the right power band. They also don't get going quite so fast so they don't have to slow down as much for the corners keeping their cornering speed up more then I can. Lastly they have full blown suspension and I have pretty much stock forks and rear shock. I have made improvements this year from last and it has helped, I added a four piston Brembo and a 260mm rotor as well as a JLF one inch longer rear aluminum swingarm. For next year I hope to add a rear Ohlins shock set up properly for me and have my front forks reworked with stiffer springs. Even after all that they will still be hard to beat on the kart tracks however they are all mine when it comes to full road courses.