Cylnder and Porting pictures (dial-up warning: #14 1024x768 pics)

[GPracer2500]

I'm freshening up my engine and thought throw up some pics. This is an 85' ATC250R cylinder. I bought it used and discovered the cylinder had been ported. I hadn't really gotten a good look at it until now. It's not marked so I have no idea who did the work. I'm not sure what if anything was done to the exhaust port timing. Anyone know the stock distance from the top of the cylinder to the top of the exhaust port? I'm getting approximately 42mm. The head has been machined quite a bit. I'll be measuring the squish to see where I'm at with that. I'm expecting it to come out pretty tight.

It's ~256cc with the 67.25mm piston that's going in.

I had one fella that does 250r cylinders look at it and he said it doesn't look too bad. He didn't say much specifically but did say he saw a few things that he likes to do. Although, he said he doesn't sharpen the edges at the entrance to the transfer port tunnels like that but also said it probably doesn't make much difference one way or another [shrug].

I realize evaluating a port job is hard by simply looking at a few pictures. Nonetheless, any comments?

http://i34.photobucket.com/albums/d133/gpracer2500/P9110090Large.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P9110093Large.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P9110094Large.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P9110092Large.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P9110091Large.jpg



Here's a TRX cylinder (a friends) that was purchased on E-bay that someone has been into. It's dirty, but regardless this work doesn't look too impressive. No biggie though--it wasn't purchased for the port job.
http://i34.photobucket.com/albums/d133/gpracer2500/P4040061Large.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P4040064Large.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P4040062Large.jpg


For comparison, here's the OEM port on an 86' TRX250R cylinder. Didn't get pics of the transfer tunnels.
http://i34.photobucket.com/albums/d133/gpracer2500/P4040060Large.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P4040066Large.jpg







And just for fun, check out how a CR500R cylinder compares. The 500 looks absolutely massive!
http://i34.photobucket.com/albums/d133/gpracer2500/P9110077Large.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P9110081Large.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P9110084Large.jpg

250r piston in 500 jug:
http://i34.photobucket.com/albums/d133/gpracer2500/P9110085Large.jpg

That big jug spinning this paddle should be a freakin' riot! :devil:
http://i34.photobucket.com/albums/d133/gpracer2500/P9110100Large.jpg

[mxduner]

what size is that tire?

[GPracer2500]

It's an 18" Skat-Trak Hooker 10 paddle. It looks strangely wide because it isn't mounted. The paddle blades "pull" the carcass flat when they're new and unmounted.

It will look essentially the same as this Skat-Trak Viper (on the right) once mounted:
http://i34.photobucket.com/albums/d133/gpracer2500/P9110101.jpg

[250r4life]

so you have both bikes and the ATC apart for top ends right now GP? how you coming along in your preperations? any talk about a 1st trip?

[GPracer2500]

ATC and CR500 are apart at the moment. The 500 should be done in the next week or two. The ATC just needs the top end put back together. But then there's the ATC swinger crack that needs attention. It didn't change through last season so if need be I'll ride it as-is if I run out of time. Needs to be fixed though.

CR250 piston is fresh and it's together but still needs to come apart for the frame swap. I'm waiting to finish the 500 before I tear into it. I may get the new frame powder coated and if I decide to do that I'll get the ATC swinger off and fixed so it can be powder coated as well. Just kinda feelin' my way along...

It's looking like my first trip may be Oct 12. It's gonna be a family trip for Ruf and at least one other family he knows from up north. There may be some new (read: probably slow) duners coming too, perhaps a couple on bikes which will be cool for me. The date is solid; who exactly will be there is still up in the air--I'm sure you know how that goes.

Family-type trips aren't my preferred trips. Usually there's a less serious/fast riding going on--it just depends. That will be ok though. I need to do some shake-down rides on the 500, the 500 and ATC will probably have nothing but static heat cycles in them, and I kinda want to do some testing of different compressions on the ATC. I wanna try dropping it with some thicker gaskets and see what I think. So, I should have plenty to keep my occupied.

You interested in going those dates?

[250r4life]

what did you dip your cylinders in to make them look so good?

they kinda look like the duncan top end that i had when i would get it back from getting nikasiled...

[quad janern]

im in love with that 500 cylinder :D

[250r4life]

Originally posted by GPracer2500

It's looking like my first trip may be Oct 12. It's gonna be a family trip for Ruf and at least one other family he knows from up north. There may be some new (read: probably slow) duners coming too, perhaps a couple on bikes which will be cool for me. The date is solid; who exactly will be there is still up in the air--I'm sure you know how that goes.

Family-type trips aren't my preferred trips. Usually there's a less serious/fast riding going on--it just depends. That will be ok though. I need to do some shake-down rides on the 500, the 500 and ATC will probably have nothing but static heat cycles in them, and I kinda want to do some testing of different compressions on the ATC. I wanna try dropping it with some thicker gaskets and see what I think. So, I should have plenty to keep my occupied.

You interested in going those dates?

yah... i know how all of that goes- who is exactly coming and slower riders...

most of my trips are family trips, but most of the time whoever is there can keep up just fine and we get some pretty good riding in... if there is a big discrepancy in rider capability, our camp will usually have 2 different groups- one for more of the "scenic" duning...

im not sure how thick of gaskets youre looking into, but im pretty sure i have a OEM trx gasket lying around if you want it... if i recall that is thicker than the stock ATC gasket...


if ya'll dont mind a tag-a-long, yah, i could be interested in going then... glamis or where?

[Aceman]

Originally posted by 250r4life
what did you dip your cylinders in to make them look so good?

they kinda look like the duncan top end that i had when i would get it back from getting nikasiled...

They look glass-beaded to me.

GP, your CR500 with that paddle tire is going to scream I bet. You'll probably spend more time in the air than on the ground!

[GPracer2500]

Originally posted by 250r4life
what did you dip your cylinders in to make them look so good?

they kinda look like the duncan top end that i had when i would get it back from getting nikasiled...

Not sure exactly. Gary at Custom did them. Like Aceman said, I think he blasted them with some media. The ATC cylinder was painted black. I like it a lot better now.

[GPracer2500]

Originally posted by 250r4life
yah... i know how all of that goes- who is exactly coming and slower riders...

most of my trips are family trips, but most of the time whoever is there can keep up just fine and we get some pretty good riding in... if there is a big discrepancy in rider capability, our camp will usually have 2 different groups- one for more of the "scenic" duning...

im not sure how thick of gaskets youre looking into, but im pretty sure i have a OEM trx gasket lying around if you want it... if i recall that is thicker than the stock ATC gasket...


if ya'll dont mind a tag-a-long, yah, i could be interested in going then... glamis or where?

Cool. The more the better. If we're lucky I'll have both bikes up and running so you'll be welcome to give the CR250 q wirl if you'd like.

The plan is for Glamis. Theres a specific spot on the edge of the Garbage Flats that we've camped at several times before.

Yeah, I do want the TRX gasket if you can put your hands on it. So far I've got a single layer CR gasket (that's what I've been running) and an ATC gasket. My head is cut so much I'd like to try a TRX too. We'll see what happens. If it's real hot I might save that project for another weekend.

[GPracer2500]

500 piston is in.
http://i34.photobucket.com/albums/d133/gpracer2500/P9120117Medium.jpg


I checked the squish and came up with what seems to be a massive .100". I think I want it to be about half that.

http://i34.photobucket.com/albums/d133/gpracer2500/P9120120Medium.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P9120124Medium.jpg

[250r4life]

Originally posted by GPracer2500
Not sure exactly. Gary at Custom did them. Like Aceman said, I think he blasted them with some media. The ATC cylinder was painted black. I like it a lot better now.

yah... it looks sharp!

[250r4life]

Originally posted by GPracer2500
Cool. The more the better. If we're lucky I'll have both bikes up and running so you'll be welcome to give the CR250 q wirl if you'd like.

The plan is for Glamis. Theres a specific spot on the edge of the Garbage Flats that we've camped at several times before.

Yeah, I do want the TRX gasket if you can put your hands on it. So far I've got a single layer CR gasket (that's what I've been running) and an ATC gasket. My head is cut so much I'd like to try a TRX too. We'll see what happens. If it's real hot I might save that project for another weekend.

that'd be sweet to take the CR250 for a whirl, although i dont know if i'll take you up on that...

pretty easy to get to that spot without getting stuck?

Yah- I'll find the gasket... im 99% sure I have an OEM one lying around, and Im 100% sure I have a COMETIC one... youre welcome to both of them- i'll try and remember to look in the garage tonight...

[250r4life]

you trying to go down on compression to see if that will help your top end wind out a little better, or more for the octane requirement concern, or...?

[C-LEIGH RACING]

Originally posted by GPracer2500
500 piston is in.
http://i34.photobucket.com/albums/d133/gpracer2500/P9120117Medium.jpg


I checked the squish and came up with what seems to be a massive .100". I think I want it to be about half that.

http://i34.photobucket.com/albums/d133/gpracer2500/P9120120Medium.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/P9120124Medium.jpg


Before you cut that head :eek: remember you got to kick start that monster :D .

BTW, what kind of junk CR500 parts you have laying around, looking some busted case & crank to get measurements off of.
Neil

[GPracer2500]

Originally posted by 250r4life
you trying to go down on compression to see if that will help your top end wind out a little better, or more for the octane requirement concern, or...?

To see if it will help top-end. Almost everybody tells me that too much compression slows/hurts top-end. I'd like to see for myself. I'm not trying to disprove anything; mostly I just want to know what will happen in my engine.

I know it seems worse top-end would make sense with a whole bunch of comp. But I'm suspicious the idea gets reinforced among the peeps only because it seems like it makes sense and not because it really happens in the way we think it does [shrug].

I've got a research paper published by Yamaha (The Effect of Higher Compression Ratio in Two-Stroke Engines). In their testing, power keeps going up with increased compression. Their dyno graphs weren't carried beyond the peak power rpm very far and it DOES look like the higher comp lines and lower comp lines started coming back together after peak RPM--but I can't tell if that's just because of the exhaust being used, or because the dyno runs weren't carried out as far as I'd like to see, or if extreme compression they may not have tested would show different results or what. In the conclusion they mention higher compression ratios for improving power are limited by engine knock and increased thermal load (overheating). There's no specific mention in their findings about too much compression hurting revability or power beyond those limits. Although a very thorough and well cited research project, the paper wasn't targeted at my exact situation so I do take it with a grain of salt....

I'm probably over analyzing things, as usual. But hopefully I'll be able to draw some conclusions of my own about what my engine likes. Like I said, I'm not looking to disprove anything. If lower comp than I'm currently running (~230psi) is better for me, great.

[GPracer2500]

Originally posted by C-LEIGH RACING
Before you cut that head :eek: remember you got to kick start that monster :D .

BTW, what kind of junk CR500 parts you have laying around, looking some busted case & crank to get measurements off of.
Neil

Sorry. I haven't got any parts other than a banged-up stock expansion chamber, bent PC silencer, and a bent subframe.

I'm gonna run the head as-is for now just to try and get a performance baseline. The bike is new to me so I'd like to see where I'm at before I start monkeying with it.

It does take a healthy kick! :muscle:

[250r4life]

yah i had heard that from several sources as well, and it makes sense, but like you i dont know if it is the case or not...

i had my cylinder re-ported at the same time i lessened my compression, so i couldnt really tell ya...

if it helps you, great, but even as long as it doesnt hurt you that would be great too, as not having to worry about your octane being sufficient, as well as not having that much compression working against itself in your engine is always a good thing...

[wilkin250r]

I haven't done a whole lot of side-by-side testing where the only variable is compression, so you could take my knowledge with the proverbial grain of salt.

From what I have seen, compression kills over-rev. A big low-end boost, small peak boost, but it falls off quicker after the peak.

This also makes sense with everything you have said so far. Everybody says it "seems" to hurt revs, but nobody can give you a definitive answer how. Dyno graphs show improved power all the way up to, and including, peak HP. But the dyno graphs you saw didn't show much of anything beyond peak.

It also makes sense when you think about your over-rev. The power drops off at high revs for two reasons. Your combustion effieciency drops (usually because you can't fill the cylinder properly with fresh fuel/air), and because your parasitic parameters (like friction) become greater. It requires work and energy to compress your fuel/air to a higher compression ratio. It becomes another parasitic parameter, causing power to drop off just that much faster.

[wilkin250r]

Originally posted by GPracer2500
I'm not sure what if anything was done to the exhaust port timing. Anyone know the stock distance from the top of the cylinder to the top of the exhaust port? I'm getting approximately 42mm.

I've got a cylinder that has been ported, and it measures right about 40.5mm from the top of the cylinder to the exhaust port. However, I don't know the history or porting type on this cylinder, so I don't think the info is all that helpful.

Convert the measurement to crankshaft degrees, either by calculation (using rod lenth, angles, ect ect), or by measurement (if you have a degree wheel). This would give you, and us, a much more useful number to determine what your engine characteristics are.

[250r4life]

i found both the honda and the cometic head gaskets tonight... youre welcome to both of them...

did your buddy that burned up his banshee get it back together and running? did he figure out why it burned up? i know it was low on coolant when he checked after, but coolant just doesnt dissapear, so did he blow a head gasket or....?

[GPracer2500]

Originally posted by 250r4life
....pretty easy to get to that spot without getting stuck?...

You two wheel drive?

It's not bad. I wouldn't worry about it. Maybe you wouldn't be able to park exactly where you wanted [shrug], but I doubt you'll have trouble getting pretty much were you want to be.

I made this little map for a previous trip. It's the circled area. The pink line would be the sand highway heading towards olds.

http://img380.imageshack.us/img380/126/glamisflatscroplabeledmu5.jpg

Thanks for finding the gaskets. :)

I don't think Russ ever fixed his Banshee. I'm not sure exactly. I don't really know what he did or didn't do that allowed that to happen. He's not really the best with maintenance. I joke with his brother that he needs to be on a stock 400EX for that reason. :devil:

[GPracer2500]

Originally posted by wilkin250r
I haven't done a whole lot of side-by-side testing where the only variable is compression, so you could take my knowledge with the proverbial grain of salt.

From what I have seen, compression kills over-rev. A big low-end boost, small peak boost, but it falls off quicker after the peak.

This also makes sense with everything you have said so far. Everybody says it "seems" to hurt revs, but nobody can give you a definitive answer how. Dyno graphs show improved power all the way up to, and including, peak HP. But the dyno graphs you saw didn't show much of anything beyond peak.

It also makes sense when you think about your over-rev. The power drops off at high revs for two reasons. Your combustion effieciency drops (usually because you can't fill the cylinder properly with fresh fuel/air), and because your parasitic parameters (like friction) become greater. It requires work and energy to compress your fuel/air to a higher compression ratio. It becomes another parasitic parameter, causing power to drop off just that much faster.
That all makes sense.




Originally posted by wilkin250r
I've got a cylinder that has been ported, and it measures right about 40.5mm from the top of the cylinder to the exhaust port. However, I don't know the history or porting type on this cylinder, so I don't think the info is all that helpful.

Convert the measurement to crankshaft degrees, either by calculation (using rod lenth, angles, ect ect), or by measurement (if you have a degree wheel). This would give you, and us, a much more useful number to determine what your engine characteristics are.
I'm gonna try and get a figure in degrees. I didn't think height below the deck would be very useful to know, but I thought I'd measure it just in case someone had worked with figures like that before. I suspect the port hasn't been raised much, if at all.

Any ideas how port timings are usually measured? What I mean is, do I just measure at what point the piston begins to open the exhaust port in deg ATDC? Or are figures usually given using mean port port timing (as in half way open, half way closed)?

[250r4life]

Originally posted by GPracer2500
You two wheel drive?

It's not bad. I wouldn't worry about it. Maybe you wouldn't be able to park exactly where you wanted [shrug], but I doubt you'll have trouble getting pretty much were you want to be.

I made this little map for a previous trip. It's the circled area. The pink line would be the sand highway heading towards olds.



no no, i have a Z71 and have been stuck only once (but have never had to get pulled out... knock on wood!)...

is that the place at the edge of the dunes where you have posted several pics of ya'll being parked there?

the weather report is showing a high of 81 next friday, with a low in the 60s... we're thinking of making a trip after work friday, and come home saturday sometime... any of your bikes ready to ride?

[GPracer2500]

Originally posted by 250r4life
no no, i have a Z71 and have been stuck only once (but have never had to get pulled out... knock on wood!)...

is that the place at the edge of the dunes where you have posted several pics of ya'll being parked there?

the weather report is showing a high of 81 next friday, with a low in the 60s... we're thinking of making a trip after work friday, and come home saturday sometime... any of your bikes ready to ride?

Ahhh, no worries then. Should be a piece of cake with 4x4.

No, that spot is different. This spot is way easier to get to.

I don't think I'll be able to go next weekend. If that changes I'll let you know. 81/60's sounds really nice!

[wilkin250r]

Originally posted by GPracer2500
Any ideas how port timings are usually measured? What I mean is, do I just measure at what point the piston begins to open the exhaust port in deg ATDC? Or are figures usually given using mean port port timing (as in half way open, half way closed)?

Just as the port begins to open.

Camshaft timing is different. As you know, it's measured at either 0.050" lift, or 1mm lift, because you don't get any meaningful flow when the valve is only open 0.002". It's not considered "open" at that point. 2-stroke port timing is measured the moment the piston uncovers the port.

Most commonly used is total duration. If your exhaust opens at 86 degrees ATDC, then you have 188 degrees of exhaust duration. Same with transfer duration.