Trek 4500/ GP460 now Staton 18.75 Drive

[DetonatorTuning]

I Was Just Thinking. Even If The Exhaust Points At Me, As Long As It Gas A Long Enough Tail Pipe I Can Probably Work With It. . .

if that's the case, you have one.

the one kerf mentions is about $46.00 @DDM

 

[DetonatorTuning]

soooooo, 18 or so hours after i put up pics of the verticle configuration and no comments, no warnings, no concerns etc. ?

after i was dumb enough to burn up a perfectly good engine did i slide off into the luney fringe that gets skirted around ?

somebody talk to me, wah wah !!

steve

 

[kerf]

Ok, when's that top end kit due. The fact that you leaned out indicates whatever you did to the exhaust, improved scavenge. Ugh, good job??? I guess you'll be reading plugs and not tea leaves in the future.

 

[DetonatorTuning]

top-end kit left DDM yesterday before noon USPS Priority, maybe i'll have it Sat.

i have a few other things to do til then.

thanks,
steve

 

[kerf]

Yeah, I'm heading across the county to look at a job, catch you later.

 

[DetonatorTuning]

Yeah, I'm heading across the county to look at a job, catch you later.

be safe out there buddy.

i hope to be up and running with a better report when you get back

steve

 

[DetonatorTuning]

Ok, when's that top end kit due. The fact that you leaned out indicates whatever you did to the exhaust, improved scavenge. Ugh, good job??? I guess you'll be reading plugs and not tea leaves in the future.

now that i'm home and have the time to answer more fully, i'll take up this idea that modding my pipe somehow "improved" an area of it's function.

this is just not correct. a tuned expansion chamber pipe is not configured to create scavenge. it is designed to do exactly the opposite and by length, shape and outlet size and placement actually produces waves of pressure that push unburned intake charge back into the cylinder before the piston finishes rising past the inside of the port.

SO, while my modification DID make the effective A/F ratio go lean it was not by "improvement". it was because i put a LARGE dent in the lower reduction taper just behind the outlet location, this created back pressure just past the outlet and encouraged the exhaust flow to just pass right out the silencer. it also changed the timing of what reversion wave was left to mostly miss the critical window of oppertunity to puff intake charge back into the cylinder thus going lean.

SO, how was i able to report that it seemed to be running stronger soon after this mod ? well the 2 stroke is a marvelous little piece of mecanical art in that it uses the fuel/oil mix to BOTH burn AND keep itself alive. we all know that interanl combustion engines burn a far greater mass of oxygen than the amount of gas needed to help ignite it. if you are running richer than needed to fully burn and expand the oxygen you will dampen the expansion and loose power. if you run leaner than needed you have heat related problems and loose parts fast.

this is compounded in the 2 stroke beacuse you have lube oil entering the engine WITH the A/F charge. when this mix goes thru a jet or past a metering needle there is only so much room and every molicule of oil passing means atleast 1 of fuel isn't getting thru. so we compromize the mix to the rich side to get acceptable power AND safety. this is perfect if NOTHING changes anywhere in the state of tune.

what happened to me was that i WAS tuned reasonably close to the threshold then, because of not making adjustments for the pipe mod. was running lean enough to burn the oxygen but not rich enough to protect the engine from heat and detonation. and believe me it happened FAST when i was able to get into the upper 1/3 of the rpms and hold it.

i can probably tune around the effects of the pipe mod, but as i do i WILL loss some if not all the gains i was temperarily getting.

SO, bottom line, i wrecked an otherwise good pipe AND motor for the sake of not being patient with completing my conversion to chain. i SHOULD have gotten the clearance by using another style pipe OR reshaping just the direction of the Dom.

like PAPA Burnstein Bear says in Brother Bear rides a bike ( or some such ) "let this be a lesson to you, this is what you should NOT do."

i loved reading those stories to my kids, to bad i didn't retain a single bit of it !!

steve

 

[appye]

Well, the exhaust that the engine came with only has about a quarter inch ... not enough meat to attach a hose.

Kerf, I am aware of the one from DDM, it is just that I am getting rid of my dom pipe and wanted to set up an exhaust system similar to yours. Expect another barrage of questions from me once I start working on that!

So! Who want's a gp460 dom pipe? First $125 + shipping takes it... If I feel comfortable, I will even ship it before you send money. I am just trying to make it so it wasn't a COMPLETE waste of money, and I will probably use the money to get another stock exhaust with a long tailpipe.

 

[DetonatorTuning]

take the stocker to any welding shop in your area with a good TIG man, put a 90* on , then the drop hose.

steve

 

[DetonatorTuning]

well, my top-end kit is here and i have some questions.

i'm sure i should use some sort of assembly lube when i reinstall the piston and cylinder, anyone have a recomendation ?

all tips apprec'd.

thanks,
steve