750sx Racelogic porting successful

[Waternut]

I've finally been able to work out my kinks long enough to test the porting job I did using the templates from Racelogic. Now the tricky part of this job was that Racelogic only sells port templates for the big pin motors or 96+ and this is a 92 small pin motor. In addition, Racelogic says that the templates are designed for a stock bore and I was +1mm already. This meant I would have to exceed the lines of the template a little bit but in all honesty, I didn't really extend extra for fear of going too far and 1mm isn't all that much.

My plan for this was to create more bottom end power as I rarely ever use the top end except in short bursts in a jump.

Here are some pictures of what everything looked like before the porting process. I disassembled a perfectly good motor to do this so I didn't have to bored the cylinder any further.

View looking down into the cylinder.

View looking up into the cylinder.

View looking at the bottom of the sleeves.

Here is what the bottom of the sleeve looks like with the template in place.

 

[Waternut]

The exhaust port was a little trickier because, as I said before, this template was designed for a big pin motor with a different port timing. This means that the top of the template doesn't line up with the top of the cylinder as the instructions lead you to believe. I had to line up the template in a way that would suit my needs (aka not raiding the port)...not to hard really.

Here is what the cylinder looks like with the template in place. It's hard to see because of the light but it'll be clearer in the next few pictures.

Another shot...

 

[Waternut]

You're supposed to mark the cylinder with dye or something so when you remove the template, you know where to remove material. Well I didn't have dye but a nice bright yellow spray paint works really well. After I finished, I removed the left over with acetone but you're going to hone the cylinder at the end anyway so it really doens't even matter.

Here is where I'm supposed to remove material...

Another shot...

As you can see, I'm basically supposed to widen the port, flatten out the bottom, and slightly raise the top (which I'm actually not going to do). More on that later.

 

[Waternut]

Now it's time to start cutting... Air tools make this job incredibly simple! However, if you just had a dremel tool with one of those extensions on it(so it can fit in the port), you'd be able to do everything.

First I cut the bottom of the intake off because that was easiest. I just used a sharpie marker when I marked those up.

Then I began grinding down the exhaust port. This was in the middle when I wasn't sure if I wanted to raise the sides of the exhaust port or not.

I ended up raising them based on the recommendations from users on here. As you can see, I stopped before getting carried away and didn't touch the center of the port. This is looking up into the cylinder.

 

[Foximus]

Hrmm... I did mine with a sharpie that kept coming off when i used lubricating oil on my dies. I never even thought of spray paint. Damn.


Also, something I question on mine (and yours) Should we cut the piston to match the intake skirt?

 

[Waternut]

Here it is with the actual grinding work complete.

Here it is after I honed the cylinder...for the first time.

I then decided that the exhaust ports might be too rough from just using the grinding stones. So I lightly touched everything using a slow speed with a fine sand paper cylinder. Then I used a steel wire brush at medium speed to smooth it out to an almost mirror like finish.

Another shot...

I then chamfered the edges of the ports at roughly a 10° angle as instructed. This allows the piston rings to slide easier over the window and doesn't leave a sharp edge that could break a ring. I had to buy a somewhere rounded file to accomplish this because a straight file puts gouges on the curves surfaces. After all of this was done, I re-honed the cylinder lightly because I'm OCD and wanted everything to be as perfect as I knew how.

 

[Waternut]

Hrmm... I did mine with a sharpie that kept coming off when i used lubricating oil on my dies. I never even thought of spray paint. Damn.


Also, something I question on mine (and yours) Should we cut the piston to match the intake skirt?

I did come across this question in my research. As I understood it, the piston is cut for cooling and not intake purposes. So if it's not cut initially like Wiseco's...I'd leave it alone.

 

[Waternut]

Reinstallation on the cylinder was a huge PITA by myself but I later found out this was because I ordered standard +1mm rings and Wiseco pistons require a special ring. Once I got the rings...almost a ****ing month later because N2products that I ordered the rings from said they were in stock and then just decided not to inform me that they were back ordered. I ended up overnighting the rings directly from Wiseco...that other company still won't respond to my calls or emails. Anyway, with the correct rings and some trickery, I was able to slip both pistons into the cylinder and slide it down. DON'T FORGET TO PRESSURE CHECK THE ENGINE WHEN YOU'RE DONE!!

I did not replace the pistons. Maybe I should have but I didn't think these were that bad and I didn't want to spend a few more hundred dollars on something I wasn't sure I would like...or even worse...that I might've messed up and end up blowing the engine to pieces anyway.

 

[Foximus]

Nice! well get it on the water!

 

[Waternut]

I broke in this engine on Saturday...boring!!! I must say that even taking it easy, I could tell that the engine had more grunt than it did before. On one of my 75% throttle runs, I also noticed a significant top end difference which added a new sensation of terror...and whiplash.

On Sunday I warmed it up nice and easy and then started giving it the beans. I didn't have any boats to jump but just jumping off my own wake, I could feel a significant difference! Unfortunately, I only got to play for about 20-30 minutes before my day was ended. I managed to blow my head gasket and fry my starter.

I tried to take it easy and carefully get it back to the ramp but no good. Engine overheated and I was dead in the water. I feared I had blown the engine up but once I got home, I realized the head gasket completely failed but the engine was fine. I'm optimistic that I'll have another starter and be back up and running by this weekend to jump some boats wake.

 

[Foximus]

I basically did the sport port myself... a bit changed though.


I wonder how the hell to jet now... =\

 

[Waternut]

Don't even touch the carb... Leave it exactly the way it was.

 

[WaveDemon]

Don't even touch the carb... Leave it exactly the way it was.

that is not good advice. it might work for you though, your pistons show your motor was really rich.

 

[Foximus]

Well I have no idea where to even start on my motor. Seems I was jetted to run on faulty fuel pumps which is why my motor has been so light switchy for the last.. uhh year. haha. I guess ill just run it and see what happens but damn its so hard to remove the dual 38s from my ski.

Enough about my ski. Sorry for jackin. Looks like you did a good job, I cant wait to get my motor back from being bored tomorrow afternoon.

 

[Waternut]

that is not good advice. it might work for you though, your pistons show your motor was really rich.

Well I'm not trying to lie... I am no engine builder nor am I pretending to be one. I am only relating what I've read in quite a few posts that say you don't have to rejet when porting.

I do want to clarify that those pistons are as clean as they are because of multiple other factors unrelated to my carb. I hydrolocked the engine multiple times and that caused a head gasket leak.

Don't get me wrong... I'm sure you know more about engines than I do and I figure you're just trying to help but I don't want to confuse people in thinking that my engine was overly rich before I did this.

 

[c_legaspi]

that port job looks really good. can wait till you get it broken in and read your full review of the engine performance.

 

[Waternut]

Well I'm still running 30:1 fuel just because I haven't used all 5 gallons the last 3-4 hours of riding. Although it runs like an absolute champ...when it runs lol. I've been fighting a few other gremlins unrelated to this.

Anyway, the port job was not difficult at all and the extra power is well worth it. It's hard to notice the extra power when your arms are already getting yanked but the additional hang time off of setup wakes and boat wakes is plenty noticeable. I'd rather port another motor than tune a carb. I hate tuning carbs with a passion! I will definately be doing this on my new SN over the winter.