SPECS ADDED!!!Can any of you engine builders tell me what to exect from this port job

[Dubs chops]

these are the only specs i have. i was wondering if it would be a low end or top end port job.
62T cases, 61x cylinder. Looks to be re-sleeved b/c bore only measures 80.75mm. Engine cylinder and cases have been ported. Port height measures 36.75mm from my best measurement. All engine work was done by Circuit Jet Sports in Huntington Beach, CA, who does/did alot of PJS work

 

[waxhead]

assuming alot of things ie deck height of cylinder and your measurements are correct
that is giving you about 187 degrees exhaust
it could run fine like that
I am wondering why it is 80.75 unless it was an old stroker engine cylinder

what is the height on the transfers from the top

 

[augustaf]

The exhaust port seems to have been raised by 2mm +. That's needed for high rpm operation like in racing. It might still be good though for freestyle 'cause a lot of other factors are to be considered like the width of the x/ports. I have a 62t cylinder - big bore- with an even higher ex/port in an 06 hull which has plenty bottom end.

 

[Mouthfulloflake]

Hey Augustaf,

could you give a rundown of the rest of the set up on that 62t setup?

I want to build one!

The exhaust port seems to have been raised by 2mm +. That's needed for high rpm operation like in racing. It might still be good though for freestyle 'cause a lot of other factors are to be considered like the width of the x/ports. I have a 62t cylinder - big bore- with an even higher ex/port in an 06 hull which has plenty bottom end.

 

[augustaf]

Hey Augustaf,

could you give a rundown of the rest of the set up on that 62t setup?

I want to build one!

I would not want to do this again, read on. Back in '96 when the IJSBA changed the racing classes and went to superstock, I did not want to wait for group K- Harry had just started to promote this - and bought a new oem Raider cylinder, had it bored to 84mm and ported it myself. Did not use a degree wheel, just raised the ports another mm and widened the exhaust to at least 51mm (don't remember now if more).I do remember widening (not necessarily a good thing) the transfer ports also. This engine then went into a SN and was pretty lackluster on the bottom end. Eventually as 62T or 64X cyl. became more popular I figured out what was wrong- the exhaust port is already to high for good bottom end. This would be pretty forgettable except 2 years ago I put this engine into a new round nose hull, reusing all donor parts from the SN even the pump with a YB-SC-J prop . Dang did this thing come to life now! Same dual 46's, Same ltd. pipe and enhancer, it's a real lively performer, has bottom end and all! I surely have seen a few big bore conversions using 62T

 

[augustaf]

cylinders that suck! I don't know how this fluke happened, would not want to repeat it. I now use either 61x or62t cylinders and get Linda at North West Sleeves to install their BB sleeves (like Dominator) at a height similar to stock 61x. That seems to work well consistently.If you go the NW Sleeve route just tell them to have the sleeves stick out 1mm before machining that should be good for bottom end. For a little less than $600 and your cylinder with a piston for a sample, they'll bore it to size and match up the ports, it's like getting a porting job for free.

 

[Big Kahuna]

hey Augustaf, I thought the superstock rules came into effect after the 98 season ended........ Close friend bought Tera's pro mod that was her backup ski for the 98 WF. She sold off all her Promod's after finals, he picked up the RIVA Ski that she ran in the 97 season. Craig Farley had build it up as her back up while she was racing for Mission Yamaha in 98.

 

[augustaf]

hey Augustaf, I thought the superstock rules came into effect after the 98 season ended........ Close friend bought Tera's pro mod that was her backup ski for the 98 WF. She sold off all her Promod's after finals, he picked up the RIVA Ski that she ran in the 97 season. Craig Farley had build it up as her back up while she was racing for Mission Yamaha in 98.

You are quite right, but in 96 they were predicting the end of mod and Group K jumped on the big bore band wagon That's how I seem to remember it anyway and it was Harry's posting on his site that caused me to get the 62T cylinder

 

[Dubs chops]

i dont know any other details of the engine as i do not have it in my posession yet. I just bought it from oxnard.

 

[Dubs chops]

oxnard! did you take any other prot measurments?

 

[Big Kahuna]

these are the only specs i have. i was wondering if it would be a low end or top end port job.
62T cases, 61x cylinder. Looks to be re-sleeved b/c bore only measures 80.75mm. Engine cylinder and cases have been ported. Port height measures 36.75mm from my best measurement. All engine work was done by Circuit Jet Sports in Huntington Beach, CA, who does/did alot of PJS work

Circuit Jet Sports use to do some good work, dont know if they are even around anymore......... But this is going to be a mid to top cylinder porting if it is like one I saw years ago...... all mid to top........

 

[Dubs chops]

OK another Q and i did search a bit but didnt find anything for my exact setup. i want about 180-190 compression on this motor. since the exhaust port may have been raise a mm should i go with like a 33cc dome or will a 35cc dome be fine? i am trying to raise compression to get a little bottom end back. this is correct is it not?

 

[augustaf]

OK another Q and i did search a bit but didnt find anything for my exact setup. i want about 180-190 compression on this motor. since the exhaust port may have been raise a mm should i go with like a 33cc dome or will a 35cc dome be fine? i am trying to raise compression to get a little bottom end back. this is correct is it not?

I would suggest 35cc domes for 93 octane and an expected 175-180 psi cranking pressure. Leave the 33 domes for a race gas mixture.

 

[Dubs chops]

i think all i can get around here is 91. and i think i'm gonna try 37 first and go from there, thanks for the reply though.

 

[Matt_E]

36mm from top of exh port to deck is kinda short.
Stock is 39mm I believe.
Sounds like it's geared toward mid to top end.

 

[Dubs chops]

I'll get exact measurments when I get the motor. Hopefully i can widen them out a little bit if it's not raised too much. i'll let you guys determine that though.

 

[Big Kahuna]

I do not know the specifics, but not all porting is pump gas... ie at RIVA you could get Pump Gas Porting or Race Gas Porting... I am not expert but you may want to consult with Randy, Art, TJ, Chuckie, Paul, JSU, somebody. 180 lbs compression on that setup may be in the race gas range.......

 

[Dubs chops]

Thanks big K. I will do some consulting when i get it and can measure everything.

 

[nikad58]

I have a 1.5mm spacer plate (if he wants it he can have it)

Now if he installed in on the bottom of the cylinder and decked the top 1.5mm would that help him with getting back some low end ? Would this idea also work with 760/701 62t cylinders to lower the exhaust port ? Good idea ? lol

 

[Big Kahuna]

I was thinking the same thing, have to take into account gasket thickness also.