Post by: thmike on July 11, 2012, 09:53:34 AM
I pulled the piston out and this is what it looked like today. There was aluminum built up on the nikasil at the very top of the cylinder and some on the head. No scaring to the walls, head is all cleaned up now and the aluminum just came right off the nikasil.
Jetting INFO-The bike from the factory comes with 175 main and has a 172 in it. The friend I got the bike off of used to run 50/50 race/pump in the bike at 50:1 and I'm running 32:1 pump gas. So I'm guessing she's lean. Maybe igntion is advanced. No pinging from the motor..that I can tell anyways. Runing Maxima Castor 927 oil.
This was the second time on the bike since build. First was at the track and second was trail riding with my wife and friends. Figured I could get some jetting figured out that I was having problems with at the track.
Here are the pics of the piston
Post by: 2T Institute on July 11, 2012, 10:58:06 AM
Post by: scotty dog on July 11, 2012, 12:32:46 PM
Post by: beaner on July 11, 2012, 01:12:21 PM
Post by: thmike on July 11, 2012, 01:57:56 PM
A guy on thumpertalk said there was a lot a detenation. I know TMs love race gas/pump mix at the minimum but I was hoping to get it right on pump. Does anyone know if running a thicker base gasket along with retarding the timing would prevent this?
Post by: thmike on July 11, 2012, 02:09:32 PM
175 to 172 won't be the difference between ok and seizure. My guess is either too much timing or compression and not enough octane.
It didn't seize though..thank god. lol. just lost compression.
Post by: SachsGS on July 11, 2012, 04:04:47 PM
Post by: beaner on July 11, 2012, 04:16:22 PM
175 to 172 won't be the difference between ok and seizure. My guess is either too much timing or compression and not enough octane.
It didn't seize though..thank god. lol. just lost compression.
My bad. Should have said "meltdown". Same thing applies.
Post by: thmike on July 11, 2012, 09:05:17 PM
No obvious seizure marks but lots of erosion - must be due to detonation. I would check ignition timing, either lower compression ratio or stick to race/pump gas mix and enrichen fuel mixture slightly to bring down combustion temperatures.
So go up on the main jet, take some timing away, and lower the compression. If I do all three I should be able to get rid of this detanation issue.
Post by: Jeram on July 12, 2012, 02:18:58 AM
proper way to lower the compression is by machining the head.
why dont you just try richening the jetting and take some timing away, it might be enough to take away the detonation.
then just do some test rides to check the jetting (plug chops to make sure your on the money) and at the end of ride inspect piston top and head for detonation....
perhaps go up 2 main jet sizes and see how that goes, but also dont neglect the fact that your needle and idle may or may not be lean too.
Post by: SachsGS on July 12, 2012, 05:00:10 AM
Post by: 2T Institute on July 12, 2012, 09:13:50 AM
Post by: thmike on July 12, 2012, 10:37:35 AM
I think the squish band needs attention to, I don't think rasing the cylinder is the answer as it has no mid range now.I've been thinking about the squish...But I know if thats right I will have to run race gas. I'm trying to to go to expensive with this bike. Its a 01 and more of play toy then my race bike. I won't mind a pipey bike. Heck thats fun! But what I'm gathering its 100% detanation. The motor did feel real hot. Cases wise was a lot hotter then my yz125.
Post by: arnego2 on July 12, 2012, 02:44:07 PM
Street or open dirtroad WOT requiere quite a lot on the main, tell me where is your needle at? I run 4 rth on the JD red needle and 3 rd on the OEM in my 250s.
Post by: 2T Institute on July 13, 2012, 12:00:51 AM
I think the squish band needs attention to, I don't think rasing the cylinder is the answer as it has no mid range now.I've been thinking about the squish...But I know if thats right I will have to run race gas. I'm trying to to go to expensive with this bike. Its a 01 and more of play toy then my race bike. I won't mind a pipey bike. Heck thats fun! But what I'm gathering its 100% detanation. The motor did feel real hot. Cases wise was a lot hotter then my yz125.
Was more pre-ignition than detonation. Check your squish gap and width, it maybe set for short bursts of acceleration not long WOT runs as arnego said above.
Post by: metal_miracle on July 13, 2012, 09:10:46 PM
maybe you got the thinest of them
Post by: thmike on July 14, 2012, 07:06:06 AM
Post by: Jeram on July 15, 2012, 01:57:51 AM
1. head shape (knowledgable 2T tuners can fix this for you and wont cost much), think its under 100 bucks? and if you dont like the way it performs with the new head shape you can weld it back up and remachine to take it back to exactly how it used to be. 100% reversible.
I think a few people on here will be able to recommend a decent 2T tuner in the US to do this work for you cheaply.
2. jetting
3. ignition timing (maybe or maybe not needed)
let us know how it goes!
Post by: beaner on July 15, 2012, 12:56:52 PM
Talk to the previous owner and find out why he was using race fuel in it. Maybe he knows something you don't.
People saying you need to do something about the squish is premature. You need to baseline the bike first and do a little research to determine if they are prone to preignition or detonation, and find out from the previous owner is he's made some modification that is making it this way. You made at least 2 mistakes. You didn't run the race fuel AND leaned out the jetting based on "feel". One will compound the other if you're borderline detonating. If you put it back together, make sure you have the correct piston, check the timing, double check for any air leaks (including seals), return the jetting to stock, and do a compression check to make sure you don't have some super high compression numbers. Once you know for sure what you have, then you can decide what to do with it.
Post by: SachsGS on July 15, 2012, 02:52:50 PM
Post by: TMKIWI on July 16, 2012, 07:49:50 AM
It's been my experience that many/most TMs require higher octane fuel then can be found at automotive gas pumps.
X2.
I could get a head mod done on mine to run pump gas but like the smell of avgas too much.
TM's have higher compression then the standard japper.
Post by: thmike on July 16, 2012, 09:49:50 AM
He always ran 50:1 with synthetic oil and I'm running 32:1 with Maxima Castor 927. I'm also guessing because the bike was leaned out for 50:1 and race/pump gas that it may be alittle lean
This didn't happen on 2 short rides by the way. I rode it all day at the track one day. Then all day the week after trail riding. So about 2-3 hours on the bike when it happen. I just ordered a wossner piston today.
Post by: TMKIWI on July 17, 2012, 08:22:24 AM
More oil , less fuel.
Post by: beaner on July 17, 2012, 01:31:36 PM
If you are running 32:1 you are running leaner then he was.
More oil , less fuel.
Technically this is true, but the difference is, at 50-1 you're running 98% fuel to oil (some of which will also aid combustion), and at 32-1 about 97% fuel. 1 percent seems like an insignificant difference, but how do you accurately convert this difference to a jet size?
Post by: Jeram on July 18, 2012, 02:04:53 AM
when you compound this with the 1% change due to the fuel volumes it starts to add up perhaps to a few percent.
Post by: TMKIWI on July 18, 2012, 08:01:20 AM
Technically this is true, but the difference is, at 50-1 you're running 98% fuel to oil (some of which will also aid combustion), and at 32-1 about 97% fuel. 1 percent seems like an insignificant difference, but how do you accurately convert this difference to a jet size?
Yeh I know but if the bike was on the lean side to start with and running lower octane fuel it might have bean the tipping point.
TM's love octane.
Post by: thmike on July 18, 2012, 09:11:43 AM
I'm going to retard the timing some on the TM and hopefully have some race gas for it also. I have a buddy whos going out with his friend on a Cigar boat, one of the race looking boats and he said he could get me some 114 or 110..can't remember. If its 114 i'm going to mix it with premium 3:1. 110 will be 2:1. I'm hoping for the best anyways. I'll ride it one day at the track and take the head off to inspect the piston once i'm done with the first few rides. And if it looks crappy then it will be 50/50 or getting the head modded. I think that may be my best bet but for now I'm trying to keep the budget low. I already has about 700 into this bike. But it is a TM.
Post by: TotalNZ on July 18, 2012, 10:23:06 AM
I've been told should still be ok on pump gas but i'm thinking i'm gonna have to start mixing 50/50 av gas.
Post by: 2T Institute on July 18, 2012, 10:45:38 AM
Post by: TotalNZ on July 18, 2012, 10:50:44 AM
Run much better at 0.7mm squish with reshaped combustion chamber.Yep thats what i'm thinking too, finding someone over here to do the work is another matter.
Might end up sending it over to you 2T.
Post by: 2T Institute on July 18, 2012, 11:24:37 AM
Post by: TotalNZ on July 18, 2012, 12:15:54 PM
Post by: 2T Institute on July 18, 2012, 12:18:31 PM
Post by: thmike on July 19, 2012, 05:16:41 AM
Post by: 2T Institute on July 19, 2012, 11:50:07 AM
Usualy I work on
RPM, rod length,bore,stroke, head volume, squish width and clearence gives a Maximum Squish Velocity (MSV)
Post by: thmike on July 19, 2012, 03:40:23 PM
Post by: SachsGS on July 19, 2012, 05:16:41 PM
Post by: thmike on July 20, 2012, 02:27:30 AM
Hey thmike, have you done a compression test on the TM? I'm curious what the actual readings are, I recall some 90's CR Hondas reading upwards of 200 PSI.
I have not. I just put the wossner piston in it and went with thicker base gaskets to see if I can get it to run pump without doing head mods. Yes I know I will be losing some bottom end but I would rather loose some bottom then having to run race gas all the time. If its so bad I can't stand riding it I will send the head out to get rechambered.
The bike started right away. The motor sounds a lot smoother. I think I had piston slap before so I went with a 53.97 vs the 53.95 that was in it. Only did one heat cycle tonight. Will continue some more tomorrow and retorque some bolts. I'll see if i can get my hands on a compression tester. Don't currently have one at the moment!
Post by: thmike on July 20, 2012, 06:41:46 PM
http://contour.com/stories/2001-tm-racing