KZ550 powered YZ125 project

nelson8708 wrote:

yeah, i saw those on ebay. For clearance issues i am going to use a stock header but, will probably end up modifying it. Thanks for the good news on the coil resistance. I noticed today when i removed the ign cover that there were no points. I also reset the timing chain like you suggested. That is another good idea with just welding some tabs onto the stock header to hold it on. Will probably do that since it will be the easiest way and save me probably 20$. I still need to get part of the head welded where an exhaust stud was broke off. When the bike was dropped it took the stud and the protruding aluminum part that the stud threads into. I feel like i am getting closer to the finish line. I will be ordering new fork seals this week so i can start on the fork rebuild. After that its a matter of getting front and rear sprockets (17/44), a longer chain, making a throttle cable bracket and finishing the tank.

Anyone ever run a 530 chain on a 520 sprocket? The yz rear sprocket is a 520 and the kz sprocket is 530. I put the 530 chain over the rear sprocket and didn't for see any issues but, the calibrated eye isn't always right if ya know what i mean :laugh:....

530 chain works fine on the 520 sprockets,free hp! :laugh:

The chain will have a little side-to-side slop on the sprocket, but I don't think it's a problem. When I used to build bicycles, I found using a chain that was too wide for the sprocket led to the chain twisting more. If the sprockets weren't lined up perfectly, it was more likely to come off if it wasn't the right width.

I thought the 550 front was a 16T sprocket, but my memeory isn't what it used to be.

loudhvx wrote:

I thought the 550 front was a 16T sprocket, but my memeory isn't what it used to be.

No, you memory is still there. Stock is a 16t sprocket but, because the smallest sprocket i can get for the yz is a 44T i need to get the biggest front sprocket i can find for the kz. The biggest i found so far is a 17t. If the sprocket is any smaller than a 44t then the diameter of the sprocket is smaller than the bolt pattern on the hub. So even with a 17t front the top speed is going to be around 100mph. I just hope my rear tire is going to be larger than the kz to get some mph back. I dont want to be at 6K rpm going down the interstate @ 60 mph. Defintally not going to be a long distance cruiser....i dont think the engine would last long when sustaining that high of rpm.

Your speed calculator came in handy when i wanted to see what the top speed was going to be.

What weight oil would you suggest? It seem from what i have researched that air cooled bikes like the thicker oil (mine doesn't have the oil cooler). Right now i put some 20w-50 in there but, that is more less just to flush it out. With not having an oil cooler i was thinking that 10w40 might break down quickly. What weight and brand oil do you recommend?

nelson8708 wrote:

loudhvx wrote:

I thought the 550 front was a 16T sprocket, but my memeory isn't what it used to be.

No, you memory is still there. Stock is a 17t sprocket but, because the smallest sprocket i can get for the yz is a 44T i need to get the biggest front sprocket i can find for the kz. The biggest i found so far is a 17t. If the sprocket is any smaller than a 44t then the diameter of the sprocket is smaller than the bolt pattern on the hub. So even with a 17t front the top speed is going to be around 100mph. I just hope my rear tire is going to be larger than the kz to get some mph back. I dont want to be at 6K rpm going down the interstate @ 60 mph. Defintally not going to be a long distance cruiser....i dont think the engine would last long when sustaining that high of rpm.

Your speed calculator came in handy when i wanted to see what the top speed was going to be.

What weight oil would you suggest? It seem from what i have researched that air cooled bikes like the thicker oil (mine doesn't have the oil cooler). Right now i put some 20w-50 in there but, that is more less just to flush it out. With not having an oil cooler i was thinking that 10w40 might break down quickly. What weight and brand oil do you recommend?

I cruise at 6k RPM all the time, but it's at like 75 mph. The motor doesn't mind, but it would seem wierd with the motor screaming and not moving.

I updated the speed calculator for 44T.

I use 10W40 up in Chicago. That's because the temp can drop down into the 40's in the fall. In hotter climates I would use 20W50. Actually, I run 20W50 on one of my "looser" motors. So either weight should work. My bikes all have oil coolers, though.

had to edit my previous post since i 17t instead of 16t for the front sprocket. I ordered my new fork seals and dust boost today so those are on the way also. I noticed in your calculator (crazy yz builders... :laugh: ) that you could choose a 18t drive sprocket. I have looked at a few sites and the biggest i can find is 17t.....you know anyone who has a 18t? I'm trying to get as close to the stock ratio as i can.

I think I threw in the 18 as a "just in case", but I don't think I know of anyone using one.

I'll go onto the GPZ550 forum, the racers there will know if 18 is available or not, They are always playing with the gearing.

i finished the wiring, brake pedal, and kick stand. I started on the exhaust and the way i had planed to route the center two cylinders to help give the wheel clearance is not going to work so the good news is the exhaust is done......the bad news is now i need to rake out the front end a few degrees to give me some room. Hope to have that done by the 8th......this is going to test my welding skillz

For the first season i probably wont let anyone ride it. For my safety my welding skillz are fine but, when i comes to other people's safety i don't trust my self yet.

I added 3-4 degrees of rake and moved the head tube forward about 1.25". This up coming weekend i am taking a trip to "tail of the dragon" with some buddies. I'm going to borrow my uncle's honda sabre 700 for the weekend. Depending on when i get back sunday i may try to rebuild my forks. I found a 41 tooth rear sprocket so i will be able to get close to the stock sprocket ratio of the kz. I know i have said that i will try to start it but, i want to wait so when it does start i can ride it down the street at least. So i need to get part of the head welded so i can drill and tap a new hole for the exhaust stud that got broke off. Here are a few pics i snapped during this past weekend.


^pic of a couple of the pipes bolted up (pre-raking the front end)

^stock head tube

^took a little bit of time with the cutting wheel

^mocked up checking the rake angel

^little paint

Just curious how you managed to get the sprockets to line up without offsetting the motor considering how much wider the KZ motor is? Also, what kind of wheels are you considering?

blind luck is the reasoning for the sprockets lining up so well. I figured i would have to offset it as well but, when i started to line stuff up the i go lucky and the engine is only off by about a 1/2" from center line of the frame. I'm going to be using the stock wheels......for now. Maybe one day i'll get some street bike wheels machined to fit. When my buddy had his XL650 SM he had cbr wheels machined to fit.

Here are a few pics from my trip to "tail of the dragon" i took over the weekend. I rode a 1985 Honda Sabre 700........i couldn't keep up with my buddies that were all on 06' and new crouch rockets. Even so, i still had a great time riding. Any one who rides needs to make it there at least once. Stay humble though and leave your ego at the base of the mountain......some guy was killed Saturday on the mountain.
















^tree of shame....bike parts from wrecks

P.S.
I plan on rebuilding the forks this weekend on the SM project.

Cool pics! Yeah, that place is on the list for me. Hopefully in the next season or two, i'll have time to get there.