81 gpz 1100 questions.....more power?

Hey gang,

Other than a 1136 cc kit, 33 CR's and a Kerker comp pipe. my 1100 motor is stock.
What's the easiest way to get a bit more power out of it?
Cams?...ignition? And if I do cams, do I just "re N re" the cams or is there more to it?

Not sure but just want a bit more power here without pulling the motor apart for head work.

Any suggestions would be great. Thanks,

Steve

NOS (nitrous)! Go big or go home!

Tall order to add more power from where you are today without going into the engine. Cams will add power but you will need new valve springs for anything above the most mild cams so you gotta crack the engine open... And if you are going to do that then you may as well have the head ported.

Nessism has it right...but the easiest 'drop-in' cams are the 1983/84 GPz1100 stock cams...sometimes difficult to source.

Am guessing that the slight power increase from "hotter cams" will be closer to red-line rpm, and perhaps improve drag race performance just enough to make the difference between winning and losing.

The most noticeable downside may be some loss of lower rpm torque. At least that was my experience.

Good Fortune!

Ok,

I think I want to stay away from NOS, and won't be drag racing much anyway
I'm looking for that roll on power/torque if possible, don't want to loose any bottom end.

I'm wondering if maybe the better idea is to buy a properly ported head with cams and springs already done.
From someone that knows what he's doing.

Then I'll sell my stock head maybe.

Another option anyway.

Bigger cams typically give up some on the bottom. Try contacting Larry C. and see what he has to say. Sounds expensive.

As mentioned, bigger cams will shift the power peak further up the rev range, even bigger ports will do the same thing, clean up the inlet tracts and polish the exhaust ports {don't polish the inlets}. The CR33's don't help bottom end performance either, they are designed to work with peak power, RS Mikuni's could have better bottom end response due to the accelerator pumps, they are also infinitely more tunable , aftermarket fuel injection is better if you really like to fiddle ... Blueprint the engine, I'm surprised no one has mentioned this, there are good HP gains to be had from a well balanced engine and then degree the cams.. Once you get to a certain level, HP gains become very expensive. They are getting 150HP+ out of the period 5 GPZ race bikes here in Australia, but its expensive...

Have you done a compression test?
How much tuning have you done to the engine?


.

Thanks 750 R1 for that advice.

And the compression test I haven't bothered with since it's pretty much a fresh rebuild since the 1136 kit. about 600 miles now I think.

No tuning at all, I pulled the plugs and they seemed to look very nice (according to an online plug photo list)

I don't know much about tuning or that sort of thing. Timing has not been checked.
I do get a bit of a cough sputter, if opening it up too fast.
Then it comes on at full throttle quite well to 9k ish. But I usually shift at 8500 when really going hard.

I should look at the jets and tubes etc in the carbs and see if they are right for the motor?
maybe and check the timing too... does that sound like a plan? Maybe that's all it needs?

I'm a woodworker not a mechanic,... before anyone blasts me.

Larry Cavanaugh would be a good choice to guide you to what you are looking for, but you can't gain much without pulling the head off the engine, sorry.

[strike]What engine is that? The 82-83 KZ1000R bored to 1136 with new sleeves? Or is it the 84 1100R or the 1000 fitted with an 1100 stock block bored to 1136?[/strike]...... Ignore that, I thought it was a "real one" by the avatar picture....

Basically, anyone who wants to answer needs to know exactly what cams, rods (17 or 18 mm), pistons (CR, make), and head you have now. [strike]If you look at the bottom front corner of the engine, you will see a number cast into a small pad, either 998 cm3 or 1089 cm3.[/strike] You also have to determine which type of cylinder head you have - the stock '81 GPz / "J" or late model "GPz Bathtub". Do you know what the 1136cc kit (I assume that is MTC) compression ratio is? Top end HP cams with long-ish duration like high compression ratios.

You are going to want to have your crankshaft re-built with a proper Torrington thrust bearing installed, trued, and welded - trust me on this one!

If you are going for mid-range torque, you probably want compression and porting matched to mild-ish cams - again, talk with Larry C.

If you are going strictly for bottom end grunt, you may want some of the "torque-est" cams - the stock ones from the 81-83 A model shaft 1100's....

Nitrous can be o.k. if used only [strike]occasionally[/strike]....rarely....

Wow Kray-Z, you know you're stuff.

Yes my bike is a full clone based on an 81 gpz.
I was told it's a stock 81 GPZ 1100 motor but the brand of bore kit in there, I just don't know.
Stock cams I assume.

Can try and find out more though.

Coast Steve wrote: Wow Kray-Z, you know you're stuff.

Yes my bike is a full clone based on an 81 gpz.
I was told it's a stock 81 GPZ 1100 motor but the brand of bore kit in there, I just don't know.
Stock cams I assume.

Can try and find out more though.

Yes, find out as many specific details about your engine as you can.

Then contact Larry Cavanaugh (Cavanaugh Racing Heads) with the list and also a list of what your engine performance goals and priorities are (be realistic and honest) and let him suggest what needs to be done and what budget you should anticipate.

I strongly recommend you have your crankshaft re-build, trued, and welded before investing in any further performance engine work.
I have had work done by Falicon (Sean Leonard), but there are others. Recently Paul Gast (Fast by Gast) supplied my buddy with a beautiful race prepped new GPz1100 18 mm wrist pin crank for a very reasonable price. Also see Nessism's (Ed's) post which I've copied below for alternatives to have your crank re-built.

Basically, all stock KZ / GPz pressed together crankshafts have a weakness in the design and construction of the thrust bearing, which is a cheap thrust washer. When this part fails, it tends to wreck the crankshaft main roller bearing near it - which pretty much sends the crank to the scrap heap. Specify to who ever is rebuilding the crank that you want a Torrington (roller bearing) thrust bearing installed, the crank checked and re-built, trued, welded, and balanced. Another weakness that seems to have been worst with '81 cranks in particular is twisting of the crankshaft under high loads or shock loads to the driveline. The twist usually occurs between cylinders 2 & 3 or 3 & 4. Welding will cure that. Also have the alternator rotor taper checked and repaired or replaced if needed. You don't really need anything else unless you are racing or plan on spinning past 10,000 RPM. If you supply a good crank it shouldn't cost more than $700 for the work....

Nessism wrote: My understanding is that Stan Gardner www.grccranks.com/ and John Pearson in Ohio are the best crank guys there are. Far far superior to Falicon these days. I'd hit them up and find out what's involved with fixing your crank. Pretty good chance they have good spare parts to offer too.