four corner scoring on piston

[guen84]

i recently took my 51mm mini stroke top end apart, found major four corner scoring and carbon build up on under side of piston. sounds to me like a too hot of a plug? running a ngk br8hs, if anything the plug looks fouled not overheated. any one have any ideas?? been having high temp issues since i built it. was getting soft seizes till i started running castor 927, now my temps just get to 425 degs.

and before any one ask my jets are way huge, running 158 main and 58 pilot in 28mm oko
running 93 octane 32:1. compression 155 if theres a air leak some where i cant find it checked crank seals n everything. running out of ideas, maybe port durations, too hot plug, or some how ignition timing is advanced. any help would be appreciated...

[bakaracer]

i recently took my 51mm mini stroke top end apart, found major four corner scoring and carbon build up on under side of piston. sounds to me like a too hot of a plug? running a ngk br8hs, if anything the plug looks fouled not overheated. any one have any ideas?? been having high temp issues since i built it. was getting soft seizes till i started running castor 927, now my temps just get to 425 degs.

and before any one ask my jets are way huge, running 158 main and 58 pilot in 28mm oko
running 93 octane 32:1. compression 155 if theres a air leak some where i cant find it checked crank seals n everything. running out of ideas, maybe port durations, too hot plug, or some how ignition timing is advanced. any help would be appreciated...

155psi for compression is to high for pump gas. You need to add a head gasket and lower that compression. As for air leaks, the common area is the exhaust flange where it connects to the bore. I use the Mr.gasket exhaust paper sheet and cut my own. You also need to retighten the nuts a few times. After heat cycles, after cool down over night , then again after riding or heat cycle.they seizing on the corners could also be caused by clearance issues being to tight from the factory. On the taiwan bores I run a flex hone throught the bore in both directions to massage the port windows and clearance the cylinder a little. I then round the edges of the piston and put an angle around the skirt of the piston on the cylinder wall side so on the down stroke it grabs oil to help lube better.

[Wheelman-111]

Greetings:

155 is crazy-high for pump gas, Dawg. I was running 125 or so and still managed to hard-seize after a long coast-down using 60/160 jetting. Your jets aren't as big as you think for that setup.

Baka-san recommends beveling the piston skirts and ball-honing the bore to remove oil-scraping sharp edges and keep the piston lubed. In retrospect, I wish I had done it.

[guen84]

baka, i didnt want to quote the last reply, would be pretty long. so you dont think has anything to do with plug or port duration? what about carbon build up on underside of piston. i also had a little blow by on the rings, on intake side. had bout 300 miles on kit. i did chamfer all ports and piston skirt and after constintly tightening exhaust got it to finally stop leaking. my concern is for new bore, i plan on running 115 aviation fuel in it seeing i can get it for $1.00 more a gallon from my local airport, and i now have another scoot for daily riding. so ill be running high compression i hear the fuel can support up to 180 psi. this will be the 3rd bore i but on, all had over heating issues. id like to be able to ride it without stopping and letting it cool every 20 minutes.

[guen84]

Greetings:

155 is crazy-high for pump gas, Dawg. I was running 125 or so and still managed to hard-seize after a long coast-down using 60/160 jetting. Your jets aren't as big as you think for that setup.

Baka-san recommends beveling the piston skirts and ball-honing the bore to remove oil-scraping sharp edges and keep the piston lubed. In retrospect, I wish I had done it.

evry time i mention them jets in a 28mm people say im way to big n got a air leak.. i cant cruz without over heating. i can ride WOT all day, to bad traffic and stop lights wont let me. tryed moving needle up and she just bogs....

[bakaracer]

Sounds like your midrange is running really lean. The air fuel screw,needle and pilot jet all tune that area. But that 155psi compression and running 93 octane pump gas is your reason for it running hot. You jet it rich or run a lot of oil and it will still run hot from it knocking and pinging.As for the carbon building up under the piston, that's common.depending on how rich the jetting is in any part of the circuit,you will have carbon buildup. If your worried about carbon build up, run a low ash oil.

[guen84]

Sounds like your midrange is running really lean. The air fuel screw,needle and pilot jet all tune that area. But that 155psi compression and running 93 octane pump gas is your reason for it running hot. You jet it rich or run a lot of oil and it will still run hot from it knocking and pinging.As for the carbon building up under the piston, that's common.depending on how rich the jetting is in any part of the circuit,you will have carbon buildup. If your worried about carbon build up, run a low ash oil.

not worried bout the carbon, just trying to read the pistons story. ive tryed many times to tune the carb with air/fuel screw and it always tells me to down jet. then i ride it and temps sky rocket. when i get the new bore what should my port durations be? planning on running 115 octane, hoping to get away with 1 base gasket and 1 head gasket... is there a good bore to run with this 44.1 mini stroker??? i hate to say it but thats almost bolt on with this crank.

[bakaracer]

Either ruima or char mo.

[guen84]

155psi for compression is to high for pump gas. You need to add a head gasket and lower that compression. As for air leaks, the common area is the exhaust flange where it connects to the bore. I use the Mr.gasket exhaust paper sheet and cut my own. You also need to retighten the nuts a few times. After heat cycles, after cool down over night , then again after riding or heat cycle.they seizing on the corners could also be caused by clearance issues being to tight from the factory. On the taiwan bores I run a flex hone throught the bore in both directions to massage the port windows and clearance the cylinder a little. I then round the edges of the piston and put an angle around the skirt of the piston on the cylinder wall side so on the down stroke it grabs oil to help lube better.[/quote]


with this flex hone i dont need to get in there and chamfer the ports? i usually go at it with the ole ladys nail file and some sand paper. if i get this hone this will take care of the ports???

[maddog]

defiine the term" mini stroker"

[guen84]

defiine the term" mini stroker"

Well its deffinetly not a full stroker, why what's your issue?

[bonesv]

defiine the term" mini stroker"

[guen84]

defiine the term" mini stroker"

exactly what i was thinking, must not be any dictionarys in the maddog house...

[Bear45-70]

i recently took my 51mm mini stroke top end apart, found major four corner scoring and carbon build up on under side of piston. .....................................................

I've wanted to ask this since you first posted this. "How did you get corners on a round cylinder and piston?"

[deuce217]

defiine the term" mini stroker"

Well muddog, there are many different types of mini strokers out there, my favorite from the list was created by your parents when they caught you looking at a dirty magazine in your room. They started calling you mini-stroker and from then on. You made a covenant with God that you would try to rid your self of this new alias, by creating an account on hondaspree.net and convincing others you are a Scooter/ 2-stroke guru. Next time you are wondering what a mini stroker is, think small and look down. I hope this helps.

Sorry to hijack the thread guen.