WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
I very much like your new technical section on your website, good job on that.
Do most of the porting specs and mods on the 1100 Yamaha also apply to the 1200 ?
Port Timing & Duration Specifications
- Thread starter #ZERO
- Start date
Do most of the porting specs and mods on the 1100 Yamaha also apply to the 1200 ?
waxhead
wannabe backflipper
- Location
- gold coast
Yes they are pretty the same engine in regards to the long block. Other than bore size. The std porting is different but the end result should be the same in timing. Just be careful on exhaust port width. As 65% of an 84 mm bore is a a lot more on an 81mm bore
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
Thanks I always thought that there was a lot more power hiding inside of that 1100 -1200 powerplant
Wax I believe you posted that the templates are 195 degrees on a stock height cylinder and 192 or something like that on a shaved zero deck cylinder so I assume you mean shaving the bottom.
I'm wondering which way you're going to run it in your motor and also what transfer timing. I'm guessing you're raising the transfer ports either way.
I'm wondering which way you're going to run it in your motor and also what transfer timing. I'm guessing you're raising the transfer ports either way.
waxhead
wannabe backflipper
- Location
- gold coast
Hey Storbeck. It’s measured from the top of the cylinder. I normally run my cylinders with a zero top deck to get my squish right. So I will machine the top of the cylinder down. Normally the cylidner is about .7-.5 mm positive deck so the piston is sitting just below the top of the deck. The engine I am using is a 197 exhaust with a 130 transfers. The good thing is because the transfers are flat on this engine and I am looking to change the angle to get a little more top end style power it makes porting the engine easy. The exhaust port shape I am using is the 65% one as shown. Sure I could get a little more at 70% but I want the motor to last for a long time. It’s a rec/race ski
- Location
- the jetski grave yard
Dang, is zero still even alive. I was asked to contact him some time back but I head he was MIA and unreliable. WTF?
Half flip95
Formerly pondracer95
- Location
- Lake Havasu City AZ
waxhead
wannabe backflipper
- Location
- gold coast
Awesome. I will get right onto to it soon. im busy building a new race ski for our nationals in march 21. its a 760 ported cases and cylinder. Also using the template as well
waxhead
wannabe backflipper
- Location
- gold coast
Heck I dont know that one as I never really use a stock pipe. but its hard to know as its not a tuned system. I would guess about 6900 but its only a guess
Okay, using triple pipes make perfect sense. My experience with untuned exhausts had me wondering how a port that high was going to work.
Ive never dyno tested a cylinder this large. Im forced to look at dyno charts for large outboards to find max port heights for non tuned exhausts. They like to run below 180 degrees open. I know watercraft pumps start loading at higher rpm so they should be okay with a little higher exhaust ports.
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
The pipes on 760's and triples in sitdowns are fairly tuned , at least compared to a 701 stock pipe in a Superjet or a Waverunner lll or VXR , the only real improvement would be drying them out or going with a separate triple exhaust pipes , lots of plumbing, pipes going everywhere , absolute sum beach to work on and lots of places for leaks.
waxhead
wannabe backflipper
- Location
- gold coast
The 760 exhaust is actually quite effective. Riva faced significant challenges in developing a better exhaust for the 760, and while they did produce an alternative, it doesn’t offer much improvement over the stock system.
On a separate note, when it comes to triple-cylinder engines, Yamaha’s pulse-tuned exhaust is well-optimized for that configuration. Interestingly, Yamaha’s stock triple-cylinder exhaust is significantly better than the factory 1100 Kawasaki system. A general rule of thumb for pulse-tuned triple-cylinder exhausts is that the combined volume of the exhaust manifold and exhaust ports should match the engine’s displacement in cubic centimeters. This principle holds true for the Yamaha 1100—I measured it myself. However, the 1200’s system is undersized, which limits its performance. To address this, I designed/made a spacer between the cylinder and the manifold to increase the overall volume. I never had the chance to test it, though, as other projects took priority.
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I'm still a little curious how high the triple liked to rev
Don't recall how high you went on the duration on the triple but I think it was in that 195 or a bit more range right?
I have a friend with a b1 that runs the stock 760 exhaust and a rear water box with a motor that has kind of the usual mods, porting and compression and zeel and 44's. Nobody can believe how well it runs with that exhaust.
Don't recall how high you went on the duration on the triple but I think it was in that 195 or a bit more range right?
I have a friend with a b1 that runs the stock 760 exhaust and a rear water box with a motor that has kind of the usual mods, porting and compression and zeel and 44's. Nobody can believe how well it runs with that exhaust.
waxhead
wannabe backflipper
- Location
- gold coast
I would have to go back through the article i wrote to say how high but 195 would seem about right. I cant remember how high it revved but it didn't mind it that's for sure. I have a friend who is running the stock 760 exhaust on his free ride ski and it works really well
- Location
- the jetski grave yard
Man I wish somebody that knew wtf they were talking about would come on here and set the record straight. This is a case of the blind leading the blind. All these guys coming off as the current experts were just on other forums asking the dumbest questions some years back. Suckers. I know the real gurus dont bother tho. I saw them phase out years ago.
Im sure all those "gurus" made race winning setups. I am 100% sure that a pro-mod or super stock ported cylinder will NOT be very snappy on pump gas. Nor will it like to sustain peak rpm for a long time on cheap gas. There is not even an out of the box impeller available that is pitched low enough for a high port/low compression cylinder. It takes some process to find a good port height/pipe combo that is very safe with cheap gas. It takes some blade bending to find the top of the power bubble. There is a lot of info on the small Yamahas. Less on Kawasakis, which in my experience are easier to burn up. Anyone can make a ripper with high ports and high compression if they want to burn methanol and maybe some nitro in the mix.