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Time to upgrade the NSR engine - help me figure which motor to shove in! (RM85)?

SpeedyCorky

SpeedyCorky

rides minibikes;U should2
Joined
Mar 9, 2003
Location
East Bay Area
Moto(s)
are clearly addicting; so you see - it's really not my fault...
Name
key-tay
OK so i gots the time, i gots the bucks, and i gots the tools - and gots the NEED, the need, for speed! It time to get rid of that silly 50cc motor and put in something with a little more thrills

i'm thinking one of these motors:

RM85 (2003 or newer)
RM125 (03 or newer)
CRF150 (2007 or newer)
... maybe another motor? you suggest!

obviously in order of how much it would cost to get the motor, from least to greatest. i'm mostly leaning towards the RM85, as i feel the RM125 would be too much power, and the CRF150 would cost $2500... ouch. I also owned a RM85 for awhile and was very happy with the power that motor made.


So, lets focus on the RM85.....
Anyone every put one of these in a NSR? what kinda weird crap am i going to have to keep in mind when doing it (how it mounts to the swingarm etc)? is there another motor out there which makes similar power and has just as accessable replacement parts?

My goal is to get the bike to 25hp or more. swingarm upgrade comes after the motor i'm thinking


suggestions/thoughts please!
 
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if i had the money i'd go for a bored out xr100 motor. almost the same route as littletwin for his track nsr. and it has a stator wound for lights already.
 
supernes550 said:
if i had the money i'd go for a bored out xr100 motor. almost the same route as littletwin for his track nsr. and it has a stator wound for lights already.
Click to expand...

Same here, add the 145cc DOHC kitaco setup and rip the streets up on it.
 
Why not go with a 63cc kit? = 13hp

or better yet, rumour has it, there is a 72cc kit for the NSR as well. Brad, I am sure, has contact info or could hook you up ;)

The XR100 is a good idea too, but only makes 7hp stock :( not sure what a 120cc kit will give ya, but will definately be some noticable power.

Or, if you have not ends to your wallet, go with the 150r motor or do something crazy like Painter Dude did, shoe-horning that WR250 motor into his YSR :devil

Regardless, you got a tough choice to make :p
 
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awe no lil' 63cc kit...even 72 is still on the small side. i'd be using the bike for more street than race, but most of my 'street' riding is in twisty stuffs, where i'm 'racing' the motor. so i'm thinking an RM85 would be OK for the street ? couldnt it be mounted up so that it doesnt vibrate too much? would it vibrate less than a CRF150?

if i go CRF150, i'm gonna have to save a bit more... those bikes/engines are still lots of $, but yea i agree it is prolly the ideal setup.
 
SpeedyCorky said:
awe no lil' 63cc kit...even 72 is still on the small side. i'd be using the bike for more street than race, but most of my 'street' riding is in twisty stuffs, where i'm 'racing' the motor. so i'm thinking an RM85 would be OK for the street ? couldnt it be mounted up so that it doesnt vibrate too much? would it vibrate less than a CRF150?

if i go CRF150, i'm gonna have to save a bit more... those bikes/engines are still lots of $, but yea i agree it is prolly the ideal setup.
Click to expand...

you want a motor to race (hence, racing the motor :p) around the streets with?!?!........:loco

fwiw, and imho, even my derbi/metrakit 72cc YSR has more than enough power for the street. Even tho' it's only geared for a top speed of 73 mph :toothless Altho', the guys in Florida have their 72cc YSR's geared to go 80 + mph :p And actually ride them on the freeway :loco

Imo, a 63cc would be pretty practical power for the street.

Btw, keep in mind, the 80cc top-ends are no different than a 72cc kit, both a single ring piston = race type motor. Difference is, close ratio gear box.

I've heard that the 80cc motors vibrate pretty bad in the NSR. Maybe as much as they do in a YSR chassis.

In fact, Wrong Way (Mario) has an 80cc NSR (race bike). Inquire with him what the vibration is like.

What do you plan to do about lighting? Most 80/85cc motors do not have after-market lighting coils available. Not sure about the 150r motor.

Anyways, just my .02, and something to concider.
 
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an 85 will vibrate you to death in a matter of 20 minutes. Ok for a sprint race, but if you are riding on the street. Better come up with a really good anti-vibration Scheme. THe 85 in our derbi broke the motor mounts and cradle. I think it did the same in Mario's YSR frame. It is not the same setup as the dirt bike, so needs special attention. works well in a RS125 frame ( has anti vibration setup). As far as power goes. Yea baby, put in a 80 or 85 and build it to a 101 or 104 and you will have a SMOKIN monster.
 
I would stick with the Stock NSR motor and add the bbk. You already have a great pipe and a carb all you need is the bbk!

If after you put the bbk and tune it and thats not enough, then it's time for a different bike!:teeth

Seriously, doing a motor swap is a really bad idea. It will cost more than you think, you will encounter more problems than you think, and it will never be enough. You also make a rare collector bike into a frankenstien!

My advice, buy the bbk for the nsr motor and put the rest of the money in a roth ira.
 
i assume the "BBK" is the 63cc or 72cc top end for the stock NSR motor? how much $ we talking for the kit? and i'm still running the stock carb, so i'd have to get a new carb...

i remember riding a 72cc derbi and was pretty content with the power it made. is swapping in a Derbi motor a direct bolt on to the NSR? and why would a 72cc Derbi kit motor vibrate less than a stock RM85 ?!

why would putting in a RM85 have so much vibration? i used to own a RM85 and i dont remember it vibrating too much, nor do i remember the motor mounting with any special dampeners or anything :confused if one were to mount an RM85 engine in an NSR and use polyurethane mounts, would that noteably reduce the vibration? what else could be done to it to reduce vibration?

What i'm hearing is that a 2 stroke will vibrate more than a 4 stroke. i'm not quite sure why, but i'll take your guys word for it.

i'm really liking the CRF150 motor, and i feel it would really be the way to go. makes great power in stock form, is a honda motor in a honda bike (as said), and its a nice predictable, relyable 4stroke motor. if i go that route i'm gonna have to save up a bit more $, cuz it seems the easier way to do it is buy a full bike and yank everything you need then sell whats leftover. and a full bike is still running closer to $2500. and if i'm looking to spend $2500 (at least) for a CRF150, rather than $1000 for a RM85.... then it quickly becomes a question as to if i'd rather spend that $2500 plus another grand and get a full sized sportbike (which i currently lack). god damn CRF150 motor costing sooo much !!
 
The 63 bbk is about $300 at GPC. Try to contact Pierce about a bbk/carb combo deal. Would be a lot cheaper than the huge mess of motor transplant.
 
Btw, I had a talk with TylerW at the track, whom owns & tracks a Honda Expert (w/c 150r). I inquired with him the maintainance with the motor, he replied that the Xpert 150r requires a LOT more maintainance (short top-end life) vs a 150f (air-cooled) motor. However, the power between motors are very different....Xpert is a purpose built race bike.

<edit> again, if you're fixed on a 4-stroke motor, then go with an Xr100 w/ 120kit. Not sure of the 150f motor. Altho', I believe, the power would be better if you stayed with the NSR motor w/ a 63 or 72cc kit.

something other to concider ;)
 
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$300-600$ to get the NSR a bit faster and the ease of doing so is really tempting....but

i'm just really afraid i'd spend $300 for the BBK, then $250 on a carb, slap it in and get it all tuned right - then be unhappy with the power. i'm looking to make the NSR rip pretty damn good; manimal claims the 63cc kit will give 13hp... 13 hp is pretty far from my 25hp goal, but it might be *just* enough to make me happy and feel its not so damn slow, w/o going out and spending $2500 (minimal) and countless hours swapping in a CRF150

anyone out there got a NSR with a 63cc kit i could ride around to see if its gonna be enough juice? or 2nd best thing post up how you thought the power compaired to the stocker 50cc? cuz yea, for the $ and the effort, if putting in a 63kit is gonna get me satisfied with the power, then doing that is clearly the 'bang for the buck' type of fix

granted a CRF150 would be stupid powerful/fun... but again, price tag and timewise its A LOT to be putting into a lil' NSR
 
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SpeedyCorky said:
.......anyone out there got a NSR with a 63cc kit i could ride around to see if its gonna be enough juice? cuz yea, for the $ and the effort, if putting in a 63kit is gonna get me satisfied with the power, then it might be a good option.......
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Only one guy I know locally that has a 63cc kit w/ Kitaco Ignition set-up but doens't frequent barf or the track (stockton) often

However, inquire with the guys in SoCal, as there are many who race and or who have owned both (stock and modified) and prolly have the answers you're looking for.
 
^^^ ouch, $5000 for a motor w/o a carb or even electronics to make the thing work... pretty sexy motor but i think i'd rather buy another 10R for that kinda $ !


not to mention that those flat motors kinda scare me, i dunno why



so mario, clue us in as to how that NSR80 is. its a CR80 motor, yes? vibrate like crazy? or is it OK? does it make *too much* power? or do you still feel like its never enough?
 
Vibrates like crazy. I was looking at the bike yesterday after I was done going over my stock NSR.

If I can get off my ass and run a couple errands, I am going to tear down the 80 and try to rebuild the bike. I need to remove the motor cradle that cracked in several places.

It was Frankenstein cradle and the welds were not pretty. The vibration caused the motor to vibrate out of the frame while I was on the track. Even the exhaust rattled apart in places. BTW, you will have to custom fabricate a dirt bike exhaust to exit underneath and to the side, verses the traditional up and to the side MX style.

It was fun while it lasted, doing wheelies out of transitions and still trying to settle the front tire while I was almost touching a knee down. Having said all of that, if the motor in there now, which ran fine, can be torn down and rebuilt for a relatively small cost, I will rebuild the entire bike to have the 80 motor in it. I will still expect it to fail at some point though.
 
SpeedyCorky said:
$300-600$ to get the NSR a bit faster and the ease of doing so is really tempting....but

i'm just really afraid i'd spend $300 for the BBK, then $250 on a carb, slap it in and get it all tuned right - then be unhappy with the power. i'm looking to make the NSR rip pretty damn good; manimal claims the 63cc kit will give 13hp... 13 hp is pretty far from my 25hp goal, but it might be *just* enough to make me happy and feel its not so damn slow, w/o going out and spending $2500 (minimal) and countless hours swapping in a CRF150

anyone out there got a NSR with a 63cc kit i could ride around to see if its gonna be enough juice? or 2nd best thing post up how you thought the power compaired to the stocker 50cc? cuz yea, for the $ and the effort, if putting in a 63kit is gonna get me satisfied with the power, then doing that is clearly the 'bang for the buck' type of fix

granted a CRF150 would be stupid powerful/fun... but again, price tag and timewise its A LOT to be putting into a lil' NSR
Click to expand...

First, the carb won't be $250. Second, you will have to spend the time to tune no matter what route you go. Third, a bit faster is an understatement, you are nearly doubling the power of the stock motor. Any power increase that significant will make a huge difference.
 
I think your on the rite path, just wate till you can get a chance to ride someones bike with the BBK. Hell if it costs you an afternoon & a tank of gass + a bear for the guy, isnt that way better than wasting the $600 & finding out it isnt what you want? If you find you realy like it, your out only a minimal amount of cash. In my opinion its worth it.

Here is a good resorce for XR100 hop-ups if you are concidering it.
http://www.hondaminitrail.com/XR100.htm

Like I mentioned its all very expensive! You will spend as much or more building a Screaming XR100+ cc as you would on getting a good running CRF150.... Then later you could up the CRF when you decide you need more power.

But hay, just my opinion.....


When I get things settled down here with my new house Ill be puting a TTR225 or 230 motor in my YSR. Frankenbike? No! Good reliable power, Yes!
With the XR100 its a slow Frankenbike. But I have to do what I can for the time being. The House comes first. It will be worth it in the long run, My grage is 900 sq ft. :) & will give me plenty of room for the bikes.
 
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