Port Timing & Duration Specifications

[WFO Speedracer]

Here is the porting template you can down load and 3d print for your 84mm yamaha, 195 exhaust port duration on a .7 dech height yamaha engine. Your welcome
https://www.waxracingproducts.com/pages/exhaust-port-template

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 ?

 

[waxhead]

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]

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

Thanks I always thought that there was a lot more power hiding inside of that 1100 -1200 powerplant

 

[Storbeck]

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.

 

[waxhead]

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.

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

 

[Storbeck]

Spicy. I dig it.