125-200cc 2013 CR 125 W/ Scavini tuning

I almost bought a 125 in 2010 when they were left over and $3,895.00. Instead I bought the WR250 because of my size instead but always second guessed the fun I could have had on a zinger. I did have a nice YZ 125 but I never got along with it because of my height. Well last week I picked the CR125 up with a fresh top end and new V Force 3 reeds and little to no maintenance. I serviced the forks and shock and sprung both ends for a tall 210 lb guy Internally the forks and shock looked great like a low hour bike would). It also came with the classic hesitation so I immediately bought the Suzuki needle. I read through the jetting threads and didn't see much on the Scalvini pipe so if anyone has any insight on tuning a Scalvini I'm all ears. It already ran better than a well tuned fresh Pro Circuit piped 2000 KX125 that I had just restored and sold so I'm really looking forward to getting it lined out. When it's done I'll post some pics but I'm not going to focus on pretty. I bought this bike to thrash when I'm in the 125 mood and for my son to play on our freestyle ramp in my backyard when he wants 2 stroke to practice. In other words this is the adopted red headed stepchild, it will be well maintained like all my stuff but it's going to be treated mean. lol

treat it mean / and it still loves you. they are a riot.

I have been running the Scalvini piple on our 2013 CR125 but I am running the 144 kit and had Pro Circuit mill the head and port it. Nothing too radical as it will still run great on 91 octane. Echoing others on the list and the internet, I found the stock silencer provides a bit of a performance gain over the Scalvini silencer and will probably be going back to it when the snow melts. The thing that I found helpful is too realize that the Scalvini’s strength is in the mid and top and from what I have been able to discover, leverages the OEM performance for the low end.

In regards to the jetting, I played around with it a bit and followed the various recommendations on the list and even opted for a Lectron (hated it...) and ultimately bought the JD Jetting Kit. Worked wonders and worked even better after I sent the carb to RB Carb Designs for his mod. Very happy with my setup.

Enjoy!

Pull the head, machine it flat then cut the squish band at .040" or a little less if you want to bias the power more to the lower end. This will also fix the jetting problems everybody seems to have with the stock bike. I would also recommend the RB carb mods. It works incredibly well on mine. Those two things will make the bike run 100% better.

I've only used race fuel in everything 2 stroke including string trimmers leaf blowers and chainsaws for the past 8 years or so. I do plan to get the cylinder head cut for race fuel. I just checked the compression and it's a decent 162 psi. I'll do the solder squish imprint and send it off to Ice Cube/Max Power RPM.

A sign that the 125 was in the cards for me happened a couple days ago. I was truing the rear wheel and replacing a few spokes and when I went to put it back on the bike I noticed the rear brake pads were about gone. Six years ago I had ordered 3 sets of rear pads for my wr250 and didn't realize they were the wrong pads until it was too late to send them back and honestly I couldn't remember who I had bought them from. I had looked the part number up and they came up for a Husaberg FX FE so I chucked them in a parts drawer. Just so happens they are a perfect match for the CR 125. its like finding money.

Ok so an update on the 125 status. It's been super cold here and even if it warmed up it would turn the ice into the worst bottomless mud pit so I decided to not leave well enough alone and pulled the top end off to inspect things and put a ring on it if all was ok. The previous owner claimed it had a new top end and it was as close to brand new a it could be except for a small amount of ring wear so I put it all back together with a new ring.. $7 from my local parts store and some new gaskets that came with the bike in a cardboard box of assorted things the previous owner had no use for which included dog toys and a random car key. I checked the squish and the clearance was a bit too much at .062 so I plan to get that whittled down to the .025 range which I think is about right for a 125 on race fuel. One thing I didn't like was the power valve when closed didn't really have any kind of positive stop in the closed position so if anyone can explain how to set the clearance of the power valve to piston in the closed position I'd appreciate the info.

Hey Doug,

There is no adjustment on the power valve. They are limited by the retainer contacting the retainer bushing at the machined stop in the power valve chamber. If the retaining pin has oblonged the power valve itself that is where you tend to see clearance issues. This is rare in the 08 and later cylinders. You can add spacers on the shaft of the power valve between the retainer and the bushing to increase the clearance or you can machine the bushing to reduce the clearance. I don't recommend either as the washers abnormally wear the shaft and machining the bushing seems to weaken it and cause issues where bolts hold it in place. I have machined a step in the bushing just wide enough to clear the retainer and this worked the best. Carbon build up in the chamber often is the cause of enlarging clearance. You mostly see that when there is long term use of castor oils.

The power valves in this one seem to be for a 144 sized bore because they are about 1mm away from the piston and they don't close with any significant amount of spring pressure but after reading a bunch of threads on this forum that might be normal. The governor lineage is not worn but seems kind of floppy like it might wiggle around while its at low rpm and that's after I adjusted the link at the end of the slot giving it as much preload as possible. I'm wondering if a better spring might help or is it not necessary? I haven got to ride it because of the weather so maybe this isn't going to affect the performance.

Do the valves come to a fairly narrow leading edge or is the leading edge ~ 6-7 mm wide? Because there is no adjustment, Husky left a lot of clearance between the power valve and piston. It is what it is. The linkage is not a precise piece and all that wobbling is pretty normal.

I'd say it's fairly narrow definitely much less than 6-7mm. Thanks for the reply, since this is my first 125 Husky and I'm only familiar with Yamaha, Kaw, and Suzuki 125s I didn't know if the previous owner messed with it or if it was designed that way. It sounds like mine is on par with original. What got me second guessing it was that the previous owner included a cylinder in the parts box that appears to have been scuffed up by a overheated piston and then ruined with a ball hone. I thought who ever did the damage with the ball hone might have do some other monkey motion on the other parts as well.

Once I get a chance to ride this bike enough to decide if I like it enough to go all in on it I'll probably do some kind of big bore mod.

The narrower power valve is definitely the CR power valve. The power valve linkage design for the Husky is definitely a weak point.

So I’ve been making progress on the little 125 and got the Suzuki needle installed and was riding it when it started running really rich. I dropped the needle a clip and it got even worse and it began running fuel out of the overflow. I figured trash stuck in the float needle so I removed the carb bowl and had a good laugh. Ahh the things you find on used bikes.



Yes that’s the nozzle and the main jet and the main with the pickup tube attached.

I’ve been getting cabin fever due to ice and snow which is why I’ve commented on about every thread going today. So out of boredom here’s a pic of my CR 125

pure fun

Lol...looks like my garage...the CR125 sitting next to a TM...must be some sort of parallel universe thing.

Some of us just get it right.