SXR Port Timing?

[Balduccimoto]

I got a sxr motor in a AM hull it makes some decent power off the bottom end and the top end is torquey and screams. I was wondering if anyone has ever cut off the bottom of the cylinder or top of cases to actually drop the port timing and then negative cut the domes to achieve the right squish. I've had a 62t/62t this was done too and know a few other people, but never heard of this being done on a Kawi besides supertune only briefly mention doing this on the forum. I can't even find any port timing specs for them either.

I figure if I could get this port timing closer to a 61x yamaha I could always drop in a larger skat mag pump to really set it off. I think it would be interesting with the extra stroke kawi motors have, in a light weight hull, it could be a even funner combo.

 

[madness maker]

i have done it on the yamaha 760 cyls, lopped 2mm off of the cyl base.and recut the ada domes.. i have been out of the kawi game for a couple yrs now, so im not sure on the sxr cyl. my bridgeport is always willing to try new stuff though.. maybe find another sxr cyl, see if 1-2 mm can be taken off base of it..

 

[kevbo]

i have done it on the yamaha 760 cyls, lopped 2mm off of the cyl base.and recut the ada domes.. i have been out of the kawi game for a couple yrs now, so im not sure on the sxr cyl. my bridgeport is always willing to try new stuff though.. maybe find another sxr cyl, see if 1-2 mm can be taken off base of it..

A lowered cylinder will gain considerable response at the expense of power. It requires a good pump in order to gain thrust at low speeds.

 

[Balduccimoto]

A lowered cylinder will gain considerable response at the expense of power. It requires a good pump in order to gain thrust at low speeds.

When you talk about the pump, do you mean dropping the cylinder will require a good pump or the sxr drivetrain in general would need a good pump? I am not convinced the performance gains of a skat mag pump justifies a $1700 price tag.. I have run a solas mag in a superjet and the only thing I got out of it was increased hook up. Though I am curious if the larger diameter pumps would increase low end thrust? I'd like to keep this set up as simple/reliable as possible..

 

[ProSouth]

My friend builds 1100 kawis for racing and he decks the bottom of the cylinders. Runs 140 mags as far as the pump goes.

 

[wanderer1]

Why not run an Advent with 4 curves that will bring out in the motor what you want through timing advance? Cheaper than a deck and top end job with the flexibility for future expansion. If you still have the factory CDI this might be an easy plug and plug option.

 

[Balduccimoto]

Why not run an Advent with 4 curves that will bring out in the motor what you want through timing advance? Cheaper than a deck and top end job with the flexibility for future expansion. If you still have the factory CDI this might be an easy plug and plug option.

I have thought about that too, most likely on my list this Winter. The only thing is, I bought my ski used and has had a few previous owners. I doubt the motor has ever been rebuilt and I put alot of ride time/abuse on my motors every season (lots of WOT runs). I'd be tearing down to do a top end and a new crank anyways.

 

[Twinturbostang]

What comp are you running?
you should have True port and fill the cases that made my ski wake way up.

 

[kevbo]

When you talk about the pump, do you mean dropping the cylinder will require a good pump or the sxr drivetrain in general would need a good pump? I am not convinced the performance gains of a skat mag pump justifies a $1700 price tag.. I have run a solas mag in a superjet and the only thing I got out of it was increased hook up. Though I am curious if the larger diameter pumps would increase low end thrust? I'd like to keep this set up as simple/reliable as possible..

At least get a big hub swirl, its worth about 40% of the total gain. A larger diameter pump/inlet can make more thrust at very low hull speeds. This is why big pumps with big engines are so impressive. The advantage diminishes as speed increases. If you blip the throttle a lot then lowering the cyl will be a good cheap mod. For a price, high compression with programmable ignitions will get you better response and power without changing port timing. A mag pump will be worth a few more inches of altitude from a small setup wave. It requires maximum effort in the form of short lightweight hulls and custom engines/pumps in order to get enough altitude for flat water flips.

 

[Balduccimoto]

I am going to take your advice with advancing timing/compression. Im not going to change port timing because the cylinder really makes awesome power, but the response is lacking. Right now im looking at running AV gas, it's $6.50/gallon near me and can get a 30 gallon drum and either mix with 93 or run straight.

As this will be a budget build, im just going to over bore to 82.5mm and use racelogic's sport port. I am not convinced a pro's cylinder porting will get me much more gains to justify the price.. None like to disclose what I am paying for and that makes me uncomfortable. The sport sport widens the exhaust port and cuts the bottom of the sleeve by the boost port to help with low/mid range. Transfers I will only clean up any rough casting marks.

I am going to get a programmable ignition probably advent with a remote switch. If possible i'd like to leave compression at about 180 so I can run straight 93 if needed and then a more aggressive timing to run AV gas. Just not sure if leaving compression alone is worth the gains with only increasing timing.

I also want to get a aluminum flywheel, I can get a Jetinetics for pretty cheap but I have read that the magnets get weak/inoperable. I also saw the strong magnets can advance the timing. Either way; I am going to double check with a timing light to be 100% safe, but i'd hate to lose my base timing from weakening magnets. My other choice is TBM, but is a more expensive option. What would everyone recommend?

The pump I am going to leave alone ATM. To me a pump is easier mid season to change if I decide. I will just blueprint it for the hell of it. I have the stock big hub swirl prop in there.

 

[MADMAT]

Or drop it all in to a Trinity hull that weighs 100lbs less!! BAM! Korns SXR based Trinity ski rips.....and where it matters!

 

[wanderer1]

Or drop it all in to a Trinity hull that weighs 100lbs less!! BAM! Korns SXR based Trinity ski rips.....and where it matters!

Taking it out of a Carbon ROK and going into a glass Trinity is a backwards move to most.

 

[Balduccimoto]

Yeah I think he missed that part. I'm at 280 lbs rtr no gas, some wet foam in tray. I have aluminum bed plate to shave a few lbs too, gotta throw that in over winter

 

[MADMAT]

Oops yes I missed it....then it has to be pump....tune that sucker to riiip!

 

[garrcass]

I am going to take your advice with advancing timing/compression. Im not going to change port timing because the cylinder really makes awesome power, but the response is lacking. Right now im looking at running AV gas, it's $6.50/gallon near me and can get a 30 gallon drum and either mix with 93 or run straight.

As this will be a budget build, im just going to over bore to 82.5mm and use racelogic's sport port. I am not convinced a pro's cylinder porting will get me much more gains to justify the price.. None like to disclose what I am paying for and that makes me uncomfortable. The sport sport widens the exhaust port and cuts the bottom of the sleeve by the boost port to help with low/mid range. Transfers I will only clean up any rough casting marks.


I am going to get a programmable ignition probably advent with a remote switch. If possible i'd like to leave compression at about 180 so I can run straight 93 if needed and then a more aggressive timing to run AV gas. Just not sure if leaving compression alone is worth the gains with only increasing timing.

I also want to get a aluminum flywheel, I can get a Jetinetics for pretty cheap but I have read that the magnets get weak/inoperable. I also saw the strong magnets can advance the timing. Either way; I am going to double check with a timing light to be 100% safe, but i'd hate to lose my base timing from weakening magnets. My other choice is TBM, but is a more expensive option. What would everyone recommend?

The pump I am going to leave alone ATM. To me a pump is easier mid season to change if I decide. I will just blueprint it for the hell of it. I have the stock big hub swirl prop in there.

Who can't give you a set price on cylinder porting that's odd... Eric Brigham and Chris new Miller have given me set prices in the past. I am sure Eric is crazy busy. call new Miller it should be about $600 for a freestyle port if you just want a sport port what he would call a rec port it would probably be about $300 and you don't have to do he can also cut your stock head with the right squish and angle for what ever you want to run..

The flywheels takes many years for the magnets to get weak it doesn't happen overnight.. the accell have 6° advance built into them them. I would find a steel hub version or buy a brand new aluminum hub version I would be weary of running any with a aluminum hub that's just my opinion...

Advent for sure

Do you have a pump stuffer ?



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[Balduccimoto]

I have spoke to a few people, some of the popular choices and none would tell me actually what they do to the cylinder for a freestyle port job. I like to know what I'm paying for. All promised to email me a quote and never did. I never attempted to contact the people you mentioned though. I started looking at some home port ideas and sport port and looked very promising for the price.

I don't have a pump stuffer and that will be last to do. I can always do that mid season. Yea I can get a new accel from the guy I bought the ski from. He's asking 400 shipped but I can save shipping. Is it worth it? Or pay 600 for tbm?

 

[MADMAT]

Tune the pump tune the pump tune the pump! Your ski should be a complete handful to ride IMO.

 

[wanderer1]

I got everything you need sitting on a shelf :Banane01:

 

[garrcass]

this is what newmiller did to my cylinder I can't tell you specifics on what he raised lowered and wideind but I paid a little extra to have the skirts cut and chamfered and that greatly increases flow. I bet if you call him and tell him what your looking for he would tell you exactly what he would do to your cylinder.

I did the cleaning up of the cases myself its a ported small pin top end on a SXR bottom end the lower port timing of the small pin combined with the increased case volume is suposed to make it hit hard on the low end its going in a X2 race/wake jumper... I would have went with the 800 but its on its last bore

I don't know about the accell if it has 6° advance that's permanent your going to be crazy high on your advance on the top end and that's dangerous territory. I would go with a Zero lightend ring gear or total loss if you can't find a good steel hub aluminum charging flywheel.
You can pull the magnets out of a stock SXR flywheel and run it as a total loss with a stock CDI or a advent

 

[Balduccimoto]

Thanks for the info, I looking into removing the magnets from the SXR flywheel and after doing some searching it seems like a real good idea. Max in a day I burn about 7 gallons in the surf and I only have to restart tops 10 times during the day. Choppy days maybe more.

With zero lightening and drilling ring gear it comes out to 2.6 lbs .. about .4 lbs heavier than aftermarket aluminum. However, I feel like there would be less involvement checking timing and a stronger hub. Would only cost $135 also.

Looking at that porting it looks almost like racelogic's sport port except that you have a window on the bottom of the sleeve by the boost port, racelogic goes further down with the cut. From what I gathered, how far you cut determines boost port length and powerband. Did he modify the transfer tunnels or transfer port windows? The sport port leaves them alone. Im thinking thats what i'd be paying for, but idk they prefer to keep that a secret.