Replacing a mt125 elsinore cylinder

[Elsinore4ever]

I am working on bringing a 1976 MT125 back to life.Here's my question:During the teardown on the MT I have found the bore to be already .080" over. These bikes were known to be a bit on the dull side and I have heard some older CR jugs might fit.
Or would an MT 175 top end fit on this bike??
I bought the bike for $225, so I'm not afraid to try a few things to give it a little more kick.
Cheers,

 

[SpDyKen]

We set up my friend's MT 125 to full CR specs. Made for a pretty wild street bike! BTW, I'm pretty sure that we did not change the ignition. Have fun! :cool: :ride:

 

[Elsinore4ever]

Thanks buddy, this rocket to be (I hope) is stripped down for the dirt. Did you have any issues with the gearing on the 5sp. MT tranny??
I'm goin' shopping for a new top end!!!!!
Thanks,

 

[tjswigger]

I had a brand new 197? mt when I was a kid.I had a cr crank and top end on it by the time the transformation had been completed.I'm sure it can be done!
Check bore and stroke specs and other pertinant measurements.I also think the compression ratios were different.I'm not sure if the piston rings were alligned the same (you know the little pins where the rings close) use matching parts mt piston with mt cylinder,cr piston with cr cylinder you don't want to snag a ring and ruin everything.It's been many years and I don't remember all the details.I'm pretty sure they were very close to the same the mt being detuned ,compression,port timing maybe ignition?It was also oil injected not premix as I recall.
The mt and cr were quite different in powerbands.Did you check to see if you could have the cylinder resleeved?
I also see ads in the back of mx racing mags that offer cylinder repair,resleeving,plating etc.I would try to keep the stock cylinder if you can in the end you will have less headaches.
The Mt I had is the bike that started my long love affair with bikes and racing when I saw your post my heart skipped a beat!!

 

[SpDyKen]

We didn't change anything in the tranny, except, I believe, clutch springs, etc. Used the CR carb. & intake manifold; disabled the oil inj. pump & used pre-mix. We used the stock MT crankshaft & rod, no problems. Started out with the stock MT pipe; I do not recall what other pipes we experimented with. I'll try to talk to my friends and pick their brains.

Plan on working on the suspension!

 

[tjswigger]

The pipe in the picture I posted was a Hooker Header!

 

[Elsinore4ever]

All excellent posts guys. TJ, nice shot of a classic bike. I'm really pumped about the positive replies as I was concerned the CR top end wouldn't fit.Seeing that it would cost more than the bike is worth to restore it to original, (tach,speedo,lights,etc.) I think I'm going to go for the CR set-up. It's for riding, and I love the look and thin profile feel of these old Honda's. If I can get some of the HIT that I get on my 1980 CR125 I'll be grinning to much to see the trail! Hey SpDyKen, good point on the suspension. The enduro set up is real soft. I'm also assuming I'll need to fit a downswept pipe for the correct top end set-up. Let me know if you hear any pro's or cons on it. I'll be splitting the cases today to replace the gasket and oil seals.
Thanks again guys,

 

[Elsinore4ever]

Hey tjswigger, nice paint job!! What kind of paint did you use and how did the MT expansion chamber work with the cr top end??

 

[tjswigger]

Hey tjswigger, nice paint job!! What kind of paint did you use and how did the MT expansion chamber work with the cr top end??

I don't remember what kind of paint it was.This picture was taken in 1977 that's why my memory is kinda fuzzy on all the details. Believe it or not I used spray cans!I just had to have a "Red Racer". I do remember that the bike had a light-switch type powerband and felt much faster! I'm sorry I can't be more specific I've had close to 20 bikes since then.This one was the first.I would like to have a totally stock one again.Motorcycles affected the next 30 years of my life and are still at the top of my toy list!
I mentioned that it was a Hooker Header.I used the pipe on the stock cylinder and it made an overall increase in power.The stock pipe was damaged and was never used with the CR top end!

 

[Elsinore4ever]

Do you think the stock MT upswept pipe would fit on a CR exhaust flange? I've been kicking around the idea of trying to fit an older down pipe on the bike when I do the top end mod.
Right now the bottom end is going to the local bike guru for a tear down.He said the gearbox oil is either being sucked into the cylinder via a bad seal or an internal cracked case by the crank. I'm praying the seals are the problem. If not, I'll be looking for cases, which will put a BIG BUMMER on the cash situation for this project. I'll post later as to the outcome of the lower end. BTW, anyone know where to find decent parts aside from taking a beating on Ebay??

 

[Elsinore4ever]

Being too old for this crap simply isn't an option..

 

[2strokerfun]

Do you think the stock MT upswept pipe would fit on a CR exhaust flange?

Well, they both exit the same side, but I'm not sure. I'm guessing not. If I'm right, there are still plenty of options available to you to get a reasonably priced pipe. Go on this site and ask away. All questions will be answered (although not really quickly--these guys are experts, but they take their time):
http://honda-elsinore.com/

Good luck. I Love my '76 elsie

 

[Elsinore4ever]

Hi guys, the lower end is trashed and the top end is usable at best. So, because the rest of the bike is in really fair condition I'll be shoppping for a complete engine to drop in. Or sell the rolling frame as is. Does anyone know if or what year CR125 would bolt up to a '76 MT125 frame??

 

[Rotorranch]

What do you mean "the lower end is trashed"?

Cases broke? Rod hanging out?

Fix it. It's not that much money for old bikes like that. Parts are relatively cheap compared to todays bikes.

Bearings are inexpensive if sourced from a bearing supply.

If you decide not to fix it, you may be better off parting it out, rather than sell it as a roller.

I kind of like the phrase from the tv show "Car Crazy"... Don't crush 'em, restore 'em.



JMHO

Rotor

 

[Elsinore4ever]

Well, its been a while since I've posted, but I took Rotors advice and fixed the lower end.Turns out it only needed main bearings and seals,the crank had a light covering of rust which I was able to free up with penetrating oil. A new set of gaskets and what the hell, it ran!! My first rebuild so I'm proud (and surprised) that it went that well.



Elsies rock.......
Being too old for this crap simply isn't an option..[/QUOTE]