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feef
Energiser Bunny
Joined: 11 Feb 2002
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 Posted: 14:34 - 18 Jul 2005  Post subject: early YZF750 |
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edited 
Anyone got any info on earlier YZF750's?
I have a thunderace, and have aquired a spare engine that runs well apart from a munched 2nd gear. I've heard the YZF750 6 speed box fits straight into the Ace engine as a replacement for the standard 5 speed affair.
Problem is, I can't fiund any info online about the earlier YFZs. All I can find is stuff about either the 'ace or the R1.
Anyone know where I can find some bumf on these early machines?
a
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Last edited by feef on 14:38 - 18 Jul 2005; edited 2 times in total |
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bish777
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| feef |
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feef
Energiser Bunny
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| Posted: 14:37 - 18 Jul 2005 Post subject: |
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| Kickstart |
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Kickstart
The Oracle
Joined: 04 Feb 2002
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| Posted: 14:52 - 18 Jul 2005 Post subject: |
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Hi
The old 5 valve family seems to be fairly tough. The engines for the FZ750, FZ700, FZX750, FZR750, OW01, FZR1000, FZR1000 Exup, YZF750, Thunderace and GTS1000 are all very closely related.
Think the 6 speed box goes in easily. However apparently Yamaha used a 5 speed box as they didn't think the 6 speed was tough enough for the power of the 1000s (but then the gearbox is the weak spot of that engine, and still normally lasts 90~100k, so even halving the life of it is not a major problem).
When you do the job it is probably worth replacing the starter clutch (wears out eventually, but requires an engine stip to replace) and the bearing behind the front sprocket (wears out when people overtighten the chain, and also requires an engine strip to replace).
Probably worth trying the Exup Brotherhood for info, and for related fiddling with some fairly technical people try https://www.fz750.net .
All the best
Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing |
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feef
Energiser Bunny
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| yzf750r |
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yzf750r
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| Posted: 16:07 - 18 Jul 2005 Post subject: |
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Exup website
these guys maybe able to help....!
Good luck!
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| MarJay |
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MarJay
But it's British!
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| Posted: 16:08 - 18 Jul 2005 Post subject: |
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Sell the engine to Stew for his YZF! 
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yzf750r
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Kickstart
The Oracle
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| Posted: 16:37 - 18 Jul 2005 Post subject: |
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| MarJay wrote: | Sell the engine to Stew for his YZF! |
Nah, bore the YZF750 engine out and keep it revving. Guy on https://www.Fz750.net has his FZ750 Somewhat tuned and producing silly amounts of power:-
| Ticeman wrote: | As you all know, I'm a little on the impatient side sometimes. This is one of those times. You may or may not like this but, here it goes. I'm tired of waiting on back ordered parts. And since I now have all winter to dial this bad boy in, it should be ready to go by spring and be in perfect tune. And since I've been learning this new software on engine building I thought I would see what it predicted for this combination I've been wanting to try.
I pulled my 1186cc engine out of it's container a couple weeks ago and put it in the FZ. Poured some VP C14 (110 octane, leaded race fuel) into the tank, installed the 41s and put 18 discs in the SuperTrapp with a large opening end cap. Heat cycled it twice, changed the oil and filter, did a leak down test (8%) and compression test (280 psi w/no carbs). Synced it up and took it to the dyno.
The first pass series was 178.0 SAE Corrected RWHP, averaged. Down three sizes on the mains. Second series, 199.6 SAE CRWHP. One more step down. Third series, 206.2 SAE CRWHP. Jetted VERY closely to perfect for the day. These numbers are slightly down from what it said 7 years ago when this motor was last run. That could be due to a bunch of different factors butI was satisfied.
Tried a Nitrous run, seems the fuel valve was gummed closed, not a good thing but, I got lucky and didn't hurt the engine as I recognized what the problem was instantly and chopped the throttle.
Pulled the engine out, took it apart, put the 1040cc cylinder off the engine I'm currently rebuilding on (makes it 1125cc, could have just used the 1125 cylinder but, now I have a high torque 1125 engine, with an in-ported cylinder head and long rods) made a cylinder spacer plate, went with 3 base gaskets (after a couple attempts to lower the compression) to get the cranking compression down to 215 lbs so I can run 91 or 92 octane fuel. Set the cams to 105/105, heat cycled the engine 5 times over two days.
Brought it to work this morning at about 3 AM and just got out of the dyno room a few minutes ago. With stock 38mm CV carbs and near perfect jetting all the way thru, 164.9 SAE CRWHP average @ 12,200 rpm and 134.1 lb/ft of torque average @ 6600 rpm. That's only 6.8 lb/ft lower than the 1186 motor and 2100 rpm earlier too.
You'll love this, remember the flat spot the 750 engine has at about 3000-3500 rpm? This motor has 62 lb/ft of torque at 3500 rpm. lol It ain't flat. I'm flabber gasted. I would have never thought it could have had this much torque. Even Dynomation predicted 122 lb/ft @ 7000 rpm with 91 octane fuel (I must have entered something wrong into the program) and it's hardly ever wrong and to have it that low in the rpm range it's going to be wicked quick. Now I'm glad I left the R1 swingarm on it. Can you say wheelie? I can hardly wait for it to quit raining and the pavement dries up a little bit. It's cold here today too, 41 I think the thermometer said.
I haven't even played with the lobe centerlines yet. This is going to be very interesting over the next few months. The best part of all this is, it's seamless in it's power delivery. That means it will be very predictable with throttle application. Which also means that power slides will be easy to do and wheelies will be just as easy. The torque curve is just straight up to 6600 then a table top the rest of the way to the limiter, with hardly any fall off.
I have the MSD hooked up too. It starts instantly and idles perfectly. If you can't tell I'm a little excited and the adrenaline is flowing. This is great. I could give 2 cents about the HP, I'm sure by adjusting the lobe centers I can bring that up but, it's a street bike and torque rules!!!!
That amount of HP is more than my boss's Busa by 2 and the torque is almost 15 lb/ft more than his single best run. And since he and I weigh about the same and the bikes are fairly close as well, he's going to be hating life. I'm pumped!!!! |
Those are his dyno figures, but he is not impressed with Dynojet dynos, saying that they read about 10% higher than his.
Here is his web site:-
https://www.ticeman.com/index2.html
All the best
Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing |
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Old Thread Alert!
The last post was made 20 years, 308 days ago. Instead of replying here, would creating a new thread be more useful? |
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