Author Topic: Top End (Read 8055 times)

zcarlson12 · « **on:** January 14, 2015, 09:03:47 PM »

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.

zcarlson12 · « **Reply #1 on:** January 14, 2015, 09:07:51 PM »

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.

udontknowme · « **Reply #2 on:** January 14, 2015, 09:23:34 PM »

your transfer passages appear to be pretty black. probly got alot of exh blowing back down

zcarlson12 · « **Reply #3 on:** January 14, 2015, 09:34:15 PM »

I'll go take some pictures without the flash on. I think it's making it look darker.

udontknowme · « **Reply #4 on:** January 14, 2015, 09:39:13 PM »

yes it could be the camera or even shadows. pictures are decieving sometimes

zcarlson12 · « **Reply #5 on:** January 14, 2015, 09:50:23 PM »

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.

udontknowme · « **Reply #6 on:** January 14, 2015, 10:19:12 PM »

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

udontknowme · « **Reply #7 on:** January 14, 2015, 10:29:03 PM »

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

zcarlson12 · « **Reply #8 on:** January 15, 2015, 08:27:47 AM »

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.

pinned250r · « **Reply #9 on:** January 15, 2015, 09:07:35 AM »

A bore may not be necessary, a hone could do it. But either way a piston will be needed.

rablack21 · « **Reply #10 on:** January 15, 2015, 10:07:35 AM »

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.

zcarlson12 · « **Reply #11 on:** January 15, 2015, 02:57:15 PM »

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?

zcarlson12 · « **Reply #12 on:** January 15, 2015, 08:00:47 PM »

Pics of the intake side of the piston and the exhaust port.

C-Leigh Racing · « **Reply #13 on:** January 15, 2015, 08:19:02 PM »

Quote from: zcarlson12;48726

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.

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

zcarlson12 · « **Reply #14 on:** January 15, 2015, 08:57:39 PM »

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.