Another FZR400 sort of

The only thing I could see on the carbs that's not in the Foxeye kit is O Rings for the coolant/carb warmer setup. Those looked fine though.

Thanks Grey, that'll be a big help

 

Finally got that video to work



Well, things got a little carried away and i was far to slow on the camera. 2 bikes are now zero, what started as just pulling off a few of the easy bits turned into completely stripping both bikes. Hopefully no one was looking forward to pictures of stripping them down. I really wish i had taken some pictures of them side by side but i did get some measurements, the 400 is about an inch and a half narrower across the tank and three inches shorter from axle to axle.

Here is the frame on the Thundercat engine, right at home



The rear mounts are perfect



This is where the work needs to be done. Not to far off.



What are everyone's recommendations on cleaning the frame? The smooth parts are fairly easy but its the cast parts of the frame which are proving difficult. So far i have just been using degreaser and a non scratch scourer. I'm going to try some steel wool but i am wondering if some sort of aluminum cleaner would do a nice job wothout being too harsh

 

Got some things done on days off. Mounting plates are done. Took a little longer than i thought as there was a lot of double checking measurements, frame on, frame off.



I chose to go steel for the mounts. You could use alloy without fail but steel is cheap and the plates aren't all that heavy. I couldn't get M10 x 1.25 countersunk bolts locally, all i could find was M10 x 1.5. Not to worry, ran a tap through, problem solved.

On the left hand side(or right, can't remember) you have spacers





These normally give you 10mm from frame to engine, so to fit in the plate they simply slide back and presto. Now on the other side the engine fit flush against the frame. Some people have simply put the plates on the engine and made it fit as there is 10mm clearance on the far side. But i like to at least try and do things properly





A little nerve racking but it turned out well, engine fits in beautifully. Basically just reassembly now

 

Things have been a little slow lately, I've been pouring a lot of time into an old KTM I'm fixing up for my dads birthday. Anyway, i was hoping the front end was going to be a straight swap but alas, it was not meant to be. i was planning on simply using the FZR triples and slotting in the forks, wheel etc but, the FZR uses 43mm forks while the cat uses 41mm forks. I then looked at the cat triples in the FZR as the bearings are the same but the stem is about a half inch longer so that was out.

Ended up taking the last resort which was to get the stems swapped. Not a super hard job but a trip to the local machinist was required. Now, on the FZR, the stem has a small snap ring at the bottom, this goes through the bottom triple where it hits a small shoulder and is held in place. The idea is that the snap ring stops the stem being pulled out of the triple when tensioned with vibrations etc. Don't be fooled though, It's in there fairly tight. On the cat, the stem has no clip. It is pressed in then welded around the bottom.

Fairly straight forward the FZR stem was pressed out. The weld around the bottom of the cat stem was taken off on the lathe, then it was pressed out. The machinist then put the cat triple on the lathe and machined out the bottom hole roughly 2-3mm down to create the shoulder for the snap ring on the FZR stem.

This is what i ended up with





A little grind on the steering stops and she fits beautifully. This allows the entire Thundercat front end to bolt straight on. Steering lock looks ok but i'll have to wait till its all back together for a final check.

 

I will probably go USD eventually. While slightly smaller in diameter the cat front end has almost every adjustment(preload, compression and rebound) whereas the FZR front end has none. Along with adjust ability you get a front rim which is half an inch wider(you can run a 120. 110 is stock), and blue pot calipers up front. There are definitely better front ends you could use but i had this stuff, and the swap is fairly easy

 

Update Time : The Saga of the Swingarm

I was hoping that things would be easy but that is never the way. One of the big differences between FZR and YZF engines is the sprocket is spaced 8mm further out on the YZF. I thought i might get lucky and things line up but it didn't happen that way. The front sprocket sat roughly a chain width over which was just to much to try and correct at the rear end. The fix wasn't all that hard but one i was hoping to avoid.

Enter YZF swingarm. The YZF swingarm is wider at the rear to accommodate the half inch wider rim. It is also 20mm wider at the front. So basically all that's needed is to trim 10mm from each side of the front of the swingarm. I couldn't remove the old bearings without destroying them so they were replaced. The hardened shaft that runs through the center is now to long. An early FZR600 item should do the job. The next problem is the bolt size. The original bolt that runs through the swingarm arm is 20mm in diameter, the YZF item is 16mm. Easiest option is to have some bushes turned up.

End result



This puts the chain in pretty good alignment, it can be fine tuned with some washers. It does put the chin very close to the frame but so far there is no evidence of rubbing



With that problem sorted the last hurtle was the airbox. I will get some photos up soon. Basically it involved elongating the holes for the carb boots forward and fibreglassing the rest of the box to seal it up. Not a hard job but still time consuming.

From there it was basically just reassembly, Wiring harness was pretty straight forward just had to extend the wires for the solenoid, rear brake caliper is YZF but the FZR master had to be retained, YZF cluster bolted straight on, Fuel level sender swapped straight over, Taillight was just a matter of the off the old plug and soldering on the new one.

I really didn't take enough pictures as it just came together in a day but nothing was really difficult, just time consuming

 

Ride Report

So, she's on the road. Torque is very much improved. Will lift the front will under acceleration in first, not a great deal but it does lift. Mid range to Top end is very rich. I think it's a combination of a smaller airbox and no Ram Air. Bogs a little on half throttle but the top end is were the real problem is, won't accelerate past 9,000Rpm in top gear. The problem is there in all gears but is worst in top, won't go past 11,000 in first and gets worse as you go up. Will have to look at a jet kit as the standard needles are not adjustable.

Handling is great, doesn't feel any heavier with the new engine. Wider tires at each end should also mean more grip (shame there's no corners out here to test it out)

There is problems though as always. It jumps out of second under acceleration, a common problem on FZR/YZF600. The only solution is a full engine tear down and replace the worn parts(shift forks/drum can be changed through the sump but it is usually the engagement dog). This may have been the reason it was parked up originally. I will fix it one day but for now i can work around it

 

Hmmmm. I thought it was 110/70 and 150/60. The YZF rims are half inch wider on each end and it takes 120/60 and 160/60. Not sure what the go is there

I should have mentioned that the YZF swingarm is steel as opposed to aluminum for the FZR. It is also about 10mm longer so wheelbase is not effected greatly. If you ran the adjusters towards the front of the range it would be of similar length to the FZR swingarm.