Porting specs.?

[onebad800]

Anyone know some port specs to redo port timing on these little motors , mainly trying to acheive alittle more power yet maintain piston life for the most part. I wondered if just raising the exhaust port some .5mm-1mm? After looking at the cyl itself I see alot of improvemnets in removing the casting flash and carbon build up!!! Should be more responsive , match up the case to the cyl and gasket plan to doesnt look to bad now. Can I shave .010 off the head and still run pump fuel?Thanks for any advice

[jstoeckly]

Do a search for Bill Tripp -

J-

[1121racinkitty]

BILL ROCKS!!!!!!
WWW.KIDSPERFORMANCE.NET

[kidsperformance]

No matter what you do to the motor you really can't hurt them.....Like I wrote in a earlier post the stock lower rod is the main problem...and even if you update to the new rod it isn't clearanced right...once you get past that the sky is the limit on what you want to do...just don't show up to club races(WKCR.WSKRA and Minn groups) the tech police will get you....If you want to be the fastest kid in the neighborhood.....go for it....a word of caution also when you start twisting the motor in RPMs the cowlings will start to crack because of this all vibration you will be creating and you better find someone who is good with a Tig machine(welder)the cowling over the cyl. head the last time I heard was NLA and I tried talking to the tech police about making up a new cowling over the cyl. head,metal and fiberglass and they just wouldn't allow it because they thought I found some new HP....but they did say they would have to look into it for the future once all the cowlings were junk......Bill Tripp

[t-dub13]

Hey Bill, I know you don't want to give away any trade secrets, but can you throw out some mild porting specifics? Raise and widen the EXH port, raise and widen the transfers, lower the intake port (or trim the skirt), mill the head etc....? I'm assuming that some mild porting would get you DQ'd from stock and FIII and too slow for the F1, so only useful for pounding around the back yard. Because I don't have a dyno, I'd like to take some trial and error out of porting this time. Any help would be appreciated.

[kidsperformance]

Like I said you can't hurt them much...The motors need a lil more blowdown than what they have in stock form. You can raise the exhaust port about 10mm before you go out the port. There are so many factors with these motors to produce hp. and you can make a time bomb motor real easy. Port timing, clutching, ign., pipe design, chassis work, head work, squish velocity, carb size, The one I did for "Erica Ensor" was a very challanginge project. Putting a belt system in a stock chassis. It turned out great and the thing really scoots. The greatest gains in speed and ET were all in the drives. Her dad was always beating on my head I wasn't giving him enough HP....Bah....Bah....Bah.....finally the guy listened and we worked together and the results speak for themselves..I'm to a point in my life that I will build something for someones child if 1: the dad has a decent head on his shoulders and understands racing 2: the child isn't some "kamakasi pilot" and will crash things because he or she has no fear 3: racing takes alot of thinking and planning and calulating 4: it takes alot of practice. I see to many "yuppies" as you refer to that write a check and they think that puts them in the winners circle with there child. It don't work that way...but it has for some people. Like I say on my web site I wish I could turn back time with my 2 boys and go racing and I "would kick all ther a**".....again like I did back then...but it's time to move on. Erica doesn't race no more but her dad tells me it was so much special time between him and his daughter that he wouldn't trade it for anything.....that's what I like to hear....family fun.....I know i the last couple of years I was having motor issues but I have spent the last 3 yrs working them out with amazing results.....watch my web site from time to time. I'm going to be adding some things for people to view and think about and maybe purchase. But it's hard to sell something when it is not out there winning..I'm working on that...On some of my cyl I do I will sit in a chair for about 8 hrs...I do have to rest once in a while because of the carpotunnel that I have developed over the yrs of doing cyls. All my motors I design are all computer designed using TSR software...been using it for over 15 yrs...That stuff hasn't let me down yet....there are so many endless motor designs and theories. it at times gives me a headache...........Cheers Bill Tripp

[t-dub13]

Thanks for the tip Bill! I'm a little confused about the 10mm remark though. I was thinking maybe 1.5mm higher and widen the port a bit too, but I don't know what it looks like yet.

I'm amazed at how the factory just throws these motors together. Even though I haven't been into a kitty motor yet, I'm expecting that I could make the motor a lot happier by just matching and cleaning all the casting flash out of the ports. On the Suzi JR50 motor I did, the exh port was tiny and not even radiused. The transfers were all clogged with casting flash and not matched up to the cases. I also discovered that due to tolerance stack-up, there was too much room (like.055") between the squish band and the piston dome. Can you tell me what's a good squish for these suzi kitty motors?

Also, I'm betting that a lot could be gained by simply balancing the crank and reciprocating mass. Have you any experience in balancing these assemblies?

[kidsperformance]

I've raised exhaust ports up 10mm.....but you can grind out of the top of the port in the cyl finned area..Clean up the cast stuff is a plus...leave intake track a rough finish....good swireling affect...Stock squish is around .070.....shave .040 of head is safe at any rpm.....Becareful of widening exhaust port because the piston lan pins are between the exh and trans ports...don't want the ring to bulge into the port and snag.....disaster will result....Falicon cranks in Clearwater Fl. will balance and weld the cranks I think they charge around $350....they have done alot for kitty cat people.....I even hear some people are putting full circle cranks in, but I wouldn't recommend it because people don't understand crankcase compression ratios....make sure you read about the conn rod in the other post I wrote about...some people don't realize the work that goes into making them better.....we are basically working with a moped motor and trying to make grand prix power......I think I'm close...last couple of years I've found big gains.............Bill Tripp

[t-dub13]

A moped!!! Yeah, I'll mill the head and polish it up too. I just looked at the pic of the cylinder in the service manual. Looks like the exh port is wide enough already...surprising. What are your thoughts on the transfer ports? I usually clean them and widen/raise them a tiny bit. I dunno if that helps at all. I do leave them a slight bit rough for helping the turbulence. I guess in the end you want all the ports tuned for the same RPM...Or maybe staggared if you're looking for a wider powerband...

[1121racinkitty]

BILL ROCKS!!!

[kidsperformance]

yes the trans. can use more chordal width....about 3 more mm....looking from the intake side angle the left trans up about 15 degrees and the right one flat to 5 degrees.....don't want the streams hit each other and distribute the gases evenly as the piston goes to TDC....gives wider powerband.....will get back to you on the part # for the rod.....have to dig through Fibber McKees closet.......

[t-dub13]

Interesting! So by staggering the trans port angle, we're also staggering the open timing for a wider powerband. Having the inlet charges miss eachother will create more swirl too? Maybe have less inlet charge shoot out the exh port?

Abotu the chordal width: +1.5mm front and back or +3mm biased to one side?

BILL ROCKS!

[kidsperformance]

yes....If you have a good mini 90 degree head port tool....Like the one C C specialites sells(like the one I have and a 45 degree too).angle the front side of the trans just ahead of piston center....back part of the trans port to hit just before the back center of the piston...it will distrube out uniformly across the piston...* theory...will have to read piston patterns after you run it.....

[t-dub13]

Cool! Thanks Bill! Now I can't wait to get into that motor. I'll have to wait though. My son is too small to handle the stock power still. I may have to just find another one for my daughter who is older and likes to go much faster.