Wiseco

Posted at www.Maximum-Suzuki.com on January 3, 2002I

I was planning on posting this eventually and since it is a snowy day, I guess now is a good time.
For those of you that may be planning some engine work on your Kat, here are some of my experiences that may help.
For background, the bike in question is a '90 750 with about 51K miles on the odo. The bike has always been well maintained and ran great. It never used any oil or anything like that, but I decided I wanted a little more than it had to offer. After pricing a couple of new bikes and the insurance implications, I decided to take that money and put it into the old bike, since it would be painful to sell, anyway.
My original idea was to go to a big GSXR motor, but finding a good donor motor was not easy. The thing that really killed that idea was that I didn't want to spend up to a grand on a motor of questionable condition and then have to sink big bucks into it, anyway. My old motor was a known good starting point.
I spent a couple of months pricing various options and settled on a Wiseco 771 kit and porting. A buddy suggested a Franx Machine Works 907cc kit, which he installed in an early GSXR, but the price was more than I was willing to spend. An over-bore that big on the street did cause me some concern, too. I was seriously concerned about the 13:1 compression ratio of the Wiseco set-up, especially with the +5 ignition advancer, but some people on the board chilled me out. In the end, I went for the Wiseco. I found a local builder with a good reputation to do the work and had at it.
Pulling the motor was not a big deal. First, the head came off to decrease the weight that I would have to wrestle with. The head came out with the motor in the frame, but I hear that the 600 requires dropping the motor a bit to clear. I thought the frames and motor dimensions would be exactly the same, but I guess not.
To give you some idea of costs, here's what I ended up with:

Parts - $975.00
     Wiseco kit $500
     Complete gasket set $186
     Cam chain $86
     Rod/main bearings $200

Labor - $1000.00
     Porting head $600
     Boring $120
     Balancing (incl clutch) $120
     Measuring clearances, etc. $160
     Strip head & check springs $80

These prices could vary greatly, depending on the builder. I just put them in here to give you a ballpark figure. Other costs include oil, filter, plugs, etc. For this price, I got back the motor with the cylinders installed. I bolted the motor back in the frame, dropped the head on, ran oil lines, and reconnected all of the electrics.
I did consider going for cams, too, but cost was a big factor. To go to aftermarket cams and having the rockers welded, I would have been looking at another $1K. Gulp! On the advice of the builder, I stayed with the stock cams. He felt that they would be more than adequate (the Kat motors are very easily "over cammed") and reliabilty could suffer (a MAJOR consideration on this project). Once everything was all together, it pretty much fired right up. I followed the break-in routine as described here: www.brockracing.com
I initially used Castrol GTX oil, which was fine at first. After dropping that oil and adding 4 more quarts I developed some serious clutch slippage. I don't know if the Barnett clutch just didn't like that stuff or what, but after a switch to Motul petroleum, the slippage immediately disappeared. Like I said, I was worried about the high compression, but 93 octane pump gas has been no problem, so far. When the weather get's warm again, I may have to put the stock ignition rotor back in. We'll see.
While the motor was out, the frame was completely stripped and painted and I replaced the steering head and suspension linkage bearings while I was at it. The swingarm bearings looked O.K., so I just greased them up and put the arm back in.
Make sure you are meticulous about labelling everything. The whole job was supposed to take only 6 weeks (I knew that was B.S), but it was 3 months before I had everything back.
Even with plenty of pictures, notes, and labels, there were a few times where I was wracking my brain trying to remember how some things went back together.
At this point, I'm just waiting for some new main jets, then I'll be finished (with the motor, anyway). Once the carbs are right, I'll head over to the local dyno and see what I've got.
Feel free to email if you have any questions

** Update 8/4/02 **
As an update, I've put almost 4,000 miles on the motor since that post and I haven't had any problems with the high compression and the advancer. I will say that the bike is much less tolerant of stop and go traffic in the hot weather, so I just avoid those situations. After all, if a cop is stuck in gridlock traffic, it would probably be a little difficult for him to tag you for splitting lanes. Besides, if I want to sit in traffic, I'll do it in something that has air conditioning. I am more aware of oil change intervals, though. I used to let it go as much as 4500 miles between changes, but now I'll do them more often (like 2500-3000), just to be on the safe side.
Lately, I've been pondering a cam swap to really take advantage of what's been done, so far. We'll see. Maybe this winter.
In any case, I can attest to the streetability of an overbore in this motor. As a matter of fact, we will be making the ride to Virginia International Raceway to see the last round of the AMA Superbike season.

** Update 03/24/03 **
I finally got a chance to visit the dyno. Bear in mind that different dynos can show very different numbers and I won't go into correction factors. For what it's worth to you, it pulled an (actual) 106 HP and 51.7 Torque max (that is on a 65 degree day), so I'm satisfied that the jetting is close enough. For reference, this motor made right at 90 HP (in '91) with just a jet kit and K&N filter. Last summer, I tried a few pulls on a different dyno and it made about 90 HP that time also, but that was with the CV carbs, the jetting was a mile off, and the air temp was close to 100. Again, these are three different results on three different dynos, so the numbers would only show relative and not absolute gains.
As a side note, as we were strapping the bike down, the dyno operator (and owner of the shop) said that he had a short stroke GSXR (like this motor) with the same kit and it pulled about 102 HP, so I know that I'm definitely in the ballpark.