Project YZR125 "act 2"

I took the engine with me to work to find a suitable air intake boot to use with the carburetor and air cleaner I had aquired. The boot I ended up finding and using is for a BMW 320i ('80-'83), it goes from the air flow sensor to the air filter housing on the car (BMW# 13 71 1 267 145), but it fit the rear bell of the 38mm Mikuni carb perfectly. I machined an aluminum collar to go from the other end of the boot to the Uni dual-stage air filter I am using. The Uni filter is quite large for a pod style filter, it's intended application is a Honda TRX, but it fits my specifications nicely.

I welded up a new engine cradle *(with rubber engine mounts I fabricated) using a stock cradle after cutting/grinding/shaving off all the exisiting engine mounts.

YSR with '01 YZ125 motor mounted. The upper rear shock mount has been relocated approximately 4-1/4" back, and the swingarm has been lengthened 4-1/2" over stock. I changed the steering head angle, by raising the rear of the bike, to add some steering quickness back into the chassis after it was lengthened by the swingarm changes. Early testing has shown this has helped out, I just have to wait for a good day to test it at Hallett.

The pictures below are of a thermostat housing I machined out of aluminum billet, karting uses them and I thought why not, it should provide quicker warm-ups, help combat cold-seizures and stabilize the engine coolant temperatures for carburetor jetting purposes. It does add 1 lb 5ozs. of weight, though I feel the benefits make up for it. The bolts are 5mm Stainless Steel and the thermostat element is from a VW/Audi 4 cylinder application. Available thermostat heat ranges are 71*C(159.8*F), 80*C(176*F), and 87*C(188.6*F). I use the 71*C Behr unit made in Germany (VW/Audi # 056 121 11371). The thermostat o-ring seal is from a Toyota Supra '86-'92 (Toyota part # 16341-35010).

Below is the thermostat housing mounted on the YSR.

Click Here for miscellaneous project photos, they will be sorted out later as I make this site more organised.


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