TRX250R.ORG
Workshop => Engine and Bottom End => Topic started by: zcarlson12 on January 14, 2015, 09:03:47 PM
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I thought my motor was running pretty good before I saw any of this. I'm doing a frame up build and wanted to check out the motor before I put it all back together. I have two main questions. Am I safe in assuming all I need is a bore and piston? The seizure marks are making me think there is another problem. The top of the piston also makes me wonder if my timing is pre-detonating because of where the burn is, towards the intake side. When I look at the head the spark plug burn marks are also pointed back toward the intake side. I just had the bearings changed in the counter balancer and case so did I unintentionally retard the timing? Thanks for any help on this and if I need different pictures please let me know and I can get them.
(http://forums.trx250r.org/vbulletin_imports/103_4323_2017-04-18_4593.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4331_2017-04-18_1817.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4330_2017-04-18_2399.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4329_2017-04-18_6446.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4328_2017-04-18_1614.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4327_2017-04-18_5840.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4326_2017-04-18_727.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4325_2017-04-18_4514.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4324_2017-04-18_2809.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4332_2017-04-18_4289.jpg)
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This top end has 10 races (20 motos) and various practice sessions on it. VP 110 mixed at 40:1 with Klotz R50, b8es plug, 38mm a/s carb 52 pilot 180 main clip in the middle 2.5 turns out on the air screw, boyesen rad valve, uni filter and open airbox.
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your transfer passages appear to be pretty black. probly got alot of exh blowing back down
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I'll go take some pictures without the flash on. I think it's making it look darker.
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yes it could be the camera or even shadows. pictures are decieving sometimes
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You are correct, they are really dark. So by those being dark I definitely didn't have a good ring seal causing blow by? Does anyone know what these markings on the bottom of the cylinder mean? It is an ESR 310 on the 72.25mm bore.(http://forums.trx250r.org/vbulletin_imports/103_4333_2017-04-18_2983.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4334_2017-04-18_4661.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4335_2017-04-18_2640.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4336_2017-04-18_4149.jpg)
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if the ring seal was bad you would have black traveling down the sides of the piston. your rings appear to be working ok from what i can tell.
usually if the transfer passages become black that suggests exh is going back toward the crankcase. its not uncommon on stock engines because the exh and transfers generally arent matched real well. if yours is ported you might contact the shop who did the work and discuss it with them
i cant see the side of the piston but another thing that could be partly to blame is a large cutout on the piston side which lets exh back into the transfer ports
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the new pics are hard to tell whats going on. between the camera angle and shadows its hard to tell. but if you seeing black like this then its a pretty good sign whats going on
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I'll get a better pic like the one above tonight after work as well as the other side of the piston. Thanks of the help so far.
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A bore may not be necessary, a hone could do it. But either way a piston will be needed.
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Yes, you definitely need a piston. You may or may not need a bore. You might could get away with just a hone. Just need to check or have someone check your bore size. Sometimes the bore can be cleaned up with just a .001 or .0009 hone. If you have a bore man, take it to him and ask him. The front left exhaust side of the piston tends to be where pistons see some of their hottest spots. It may be possible that you were running a bit lean on your jetting or that the engine got too hot due to undercooling. It may also be that the blow by started occurring after the seizure.
The letters on the bottom of the cylinder indicate the porting. You have TRX 9 porting on the cylinder.
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Thanks everyone. I'm definitely not having the guy do the bore or hone this time that I had do this one so I'll have to start looking around. I thought that's what the 9 meant, thanks Ryan. Any thoughts on my timing question guys?
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Pics of the intake side of the piston and the exhaust port.
(http://forums.trx250r.org/vbulletin_imports/103_4339_2017-04-18_5916.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4340_2017-04-18_9133.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4341_2017-04-18_1673.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4342_2017-04-18_5252.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4343_2017-04-18_6151.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4344_2017-04-18_1729.jpg)
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I thought my motor was running pretty good before I saw any of this. I'm doing a frame up build and wanted to check out the motor before I put it all back together. I have two main questions. Am I safe in assuming all I need is a bore and piston? The seizure marks are making me think there is another problem. The top of the piston also makes me wonder if my timing is pre-detonating because of where the burn is, towards the intake side. When I look at the head the spark plug burn marks are also pointed back toward the intake side. I just had the bearings changed in the counter balancer and case so did I unintentionally retard the timing? Thanks for any help on this and if I need different pictures please let me know and I can get them.
(http://forums.trx250r.org/vbulletin_imports/103_4323_2017-04-18_5813.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4331_2017-04-18_9867.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4330_2017-04-18_4424.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4329_2017-04-18_3306.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4328_2017-04-18_6186.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4327_2017-04-18_6643.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4326_2017-04-18_5581.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4325_2017-04-18_6939.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4324_2017-04-18_3267.jpg)(http://forums.trx250r.org/vbulletin_imports/103_4332_2017-04-18_3022.jpg)
When you look at those pics close & see all that darkness, you have some serious port linking going on, or either something is blocking the pipe & building back pressure.
I see you have the new version of the ESR (Wiseco) piston, which has been machined to stop the port linking, but still your getting quite a bit. The seizure in that area, is pretty common on the Pro-x & ESR cylinder casting, simply because the 250R engines/cylinders just run hotter on that left side of the exhaust. Most all seizures of 250Rs will start there first.
Theres just way to much darkness, down in the ports of that cylinder, so need to check it out real close to see why.
Some ideas.
Port linking between the aux exhaust & main transfer ports.
Pipe build,, matched up to the porting
Type of riding you do, if the porting matches that, which TRX9 porting would be kinda in the higher rpm ranges, say upper midrange type.
Something blocking the pipe exit, like silencer core broken loose & out of place.
Even if for some reason the engine was running higher temps than normal could cause this.
It could be sometime or another, the engine got real hot & the seizure started & just got worse as it went along.
Before you put it back together, would suggest, to have someone open up the passage ways in the coolant jacket, over top of the exhaust port to allow more coolant to flow past that area & on the next new piston, have those little cooling holes drilled into the piston to cool the sleeve area between the main exhaust port & those aux ports.
Neil
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Thanks Neil. That definitely helped me understand what I'm looking at. I'll have to check the silencer core. I did re-pack it around this time last year and it may have gotten moved around. According to the temp gauge I never saw it go over 205 while I was riding it. I ride mx only and I'd say I'm full throttle a lot of the time as well. It sounds to me like a combination of all those things made this happen haha. I'll be sending it to you next week Neil.
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that piston might be the new esr version but i dont care for how they machine the sides. it might be letting exh into all 4 transfer passages but its hard to tell without putting the piston in there and looking
something neil didnt mention but the passages can turn black if you simply dont have enough blowdown area to let the exh out fast enough
im not trying to diagnose your problem, hek you may have several problems for all i know. just letting you know some of the reasons that will cause the black
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you can draw some vertical lines with a magic marker where all the port window edges are are then put the piston in the cylinder and see if all you ports are linking like this.
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Ok I'll see what I can find out about that. Thanks for the tip. I think you are right that it is a combination of things going on.
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that piston might be the new esr version but i dont care for how they machine the sides. it might be letting exh into all 4 transfer passages but its hard to tell without putting the piston in there and looking
something neil didnt mention but the passages can turn black if you simply dont have enough blowdown area to let the exh out fast enough
im not trying to diagnose your problem, hek you may have several problems for all i know. just letting you know some of the reasons that will cause the black
Your right about that piston on the machining. I wish they only had the machining like how the CR pistons are, where the machining was only behind the wrist pin. That way, the only chance of port linking would be from around the wrist pin center.
The whole problem, stems from the aux exhaust port windows being to far around in the bore & being close enough to the center to match up with the main transfers. I spent a bunch of hours trying stuff, cut sleeves & pistons in half, like a cut away, just to check what was happening.
When the linking is bad, the fresh crankcase charge is so weak, from so much being lost to early out into the exhaust, it cant keep the transfers clean & the engine ends up with more stagnet charge in the bottom end than fresh charge.
When I get his cylinder in, I'll do a degree on the ports & check that blow down.
Something else I'm really wondering, how much real performance are we gaining, from the lighting of those pistons from that machining on the sides. Would like to test one with no machining done to the sides, just to see what changes. I would gamble & say none that the average user would notice.
Neil
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What Pipe are you running ?
Is this a Stroker Motor ? 76mm ? Or stock stroke 72mm - (Neil will need to know this to calculate the amount of blow down)
:)
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LRD pipe and stock 89 stroke with the spacer plate. Thanks Langbolt.
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Is it the LRD Adjustable ?
Maybe you need to back it out a bit....(make the pipe LONGER) ....it might be in too far causing the wave to come back too soon and causing some blow back.
Just a thought.
Maybe Ahrlan can chime in.
:)
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That's a good idea! I think I did have it almost all the way in. It is the LRD adjustable.
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I didn't notice much of a difference when adjusting the pipe in or out, if any.
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I believe that the adjustment only affects a range of about 500 rpms. That's not a drastic change by any means.
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Is it the LRD Adjustable ?
Maybe you need to back it out a bit....(make the pipe LONGER) ....it might be in too far causing the wave to come back too soon and causing some blow back.
:)
that theory might be plausible if the transfers were extremely tall but i doubt thats the case here. i would guess theyre some where around 124* which isnt extreme at all so i have a hard time buying that scenario. judging by the pics it appears theres definatly linking going on, possibly between all 4 transfers and the aux exh. i suppose that may be the whole problem, although ive never had a engine with any serious linking so i really cant comment on how much black it would create.
neil i vaguely remember when i installed a 72mm wiseco in my ktm a while back and it seems like there was no side machining at all. just a round hole above the wristpin if i recall correct. the engine runs well despite the extra weight of a nearly full side skirted piston, although machining behind the pin may not be a bad idea to shave off a few more grams but im not sure the difference would be noticable. maybe, maybe not. i always thought it more important to keep the exh gas out rather than worry about a few extra grams of weight. so if it was designed correct, i wouldnt be afraid to use a full side skirt piston, infact i would almost prefer that type of design but thats just me
there may also be another reason to pay attention to how much is machined from the sides. you can see how theres a cavity between the wall and piston side when the piston drops down. i dont like this one bit. i dont know how much difference it makes if its there or not but i would rather it not be there
full sided piston vs machined out piston