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Information and stories pertaining to racing Suzuki two-strokes. Past and Present.

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Admin
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ouch

Post by Admin »

air cooled TR's ran pump. i have mine fixed at half way (armature pointing vertical) which gives approx 300cc/hr @ 6000 rpm
i run castrol R30 on pump and castrol TTS at 60:1 premix in tank using BP 100 racing fuel or avgas.

my other methanol bike runs tts on the oil pump and 60:1 castrol M pre mix.
the avgas bike looses about 4hp on the dyno due to oil loading and use BUHW surface discharge plugs to prevent fouling but never seized a bike.

as stated on the other board (north american two strokes), you should be seriously looking at fuel flow, either due to lean jetting, fuel line restriction or ridiculously small carbs.
considering that you have TR replica ports, TR pipes and heads, I cant imagine how the bike runs with 34mm carbs????

you have 2 probs, the bike has gone lean, causing your pre-ignition and holed piston, then she has seized.. no reasonable amount of oil is going to save your top end on an air cooled bike if you go lean.. its just going to burn off the cylinder walls, hence why u seized, and always on the exhaust port side!
then again it could be related to poor squish clearance, causing hot spots on your cylinder head.. do u have any pitting around your squish band?
too many possiblities. my head is starting to hurt..

Anyways, do what teazer said..go another 20-40 thou on your barrels, dont worry about the score marks too much and spend the money on some dyno time, preferably a load cell dyno and not inertia.. u need to put some load on the bike at certain rpm increments to find out exactly what the bike does when your pipes get hot and where the bike is failing.
Admin
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Joined: Wed Dec 31, 1969 6:00 pm

Post by Admin »

I really think it is an oiling problem and not jetting. Right cylinder looked fine and throughout the race weekend plugs never looked excessively lean.

The hole in the piston I'm convinced is where the seperated piston pit beat a hole thru the piston; the hole is the same diameter as the piston pin plus there's no evidence of being burned thru, just fresh metal from an exit wound of being punched thru.

I've found it very curious that there's absolutely no oil residue whatsoever in the left cylinder, base gasket area, or crankcase area.

This weekend think I'll test the oil lines to see if theres any flow; not sure now to test the oil pump. Maybe I'll remove the pump and spin it with a drill motor to see if oil eminates from both sides.
Admin
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Post by Admin »

Ralph,

In case you don't see my reply in the "where is everybody" thread in the main section. It's very likely I will have a race prepped GT500 at Mid-Ohio with nobody to ride it - barring a major miracle that gets me to the WERA round at BeaveRun June 21 to validate my race credentials for Mid-O. So if you are still interested in racing at Mid-O, let me know.

Jim
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Post by Admin »

Diamondj wrote:It's very likely I will have a race prepped GT500 at Mid-Ohio with nobody to ride it
Jim,

I was actually planning on coming to Mid-O even though I don't have a bike to ride, it's the annual Sundial party. Keep me in the loop.
Admin
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Post by Admin »

Ralph,

It's always hard to problem solve from a picture, but that hole does not appear to be punched through. To me it is clearly the result of detonation. You can see the granulation around the edges of the hole and they are rounded off from erosion. A punch through might shear off parts but would leave a raised volcano like cracked hole and you would most likely see several other signs of striking the underside of the piston.

The question now is what caused it. Clearly there was too much heat and a massive siezure and piston so hot that the pin pulled out of the soft metal.

Lack of oil could have been the casue of that surplus heat but it's unusual to detonate for a seizure. If there is an oil blockage I would also be looking at the heads for squish clearance issues and at jetting and timing and the whole fuel supply side. Might have been a float hanging up for some strange reason causing it to run lean.

The amount of damage tends to indicate two or more marginal conditions, ie partial fuel blockage AND an oiling issue etc.

If it were me i'd be checking the oiling system, adding a small amount of pre-mix as Shannon suggested and I'd go over the fueling system really carefully too.

teazer
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Mid-Ohio Vintage Motorcycle Days July 25-27, 2008

Post by Admin »

We usually have a large two-stroke group camping together each year. (Sundial and/or Smokeriders) This year the camping rules have changed. Camping sites are now sectioned off and assigned, 1 per registration. If you need more room you must reserve and pay for more than 1 site. Site assignments are given out upon arrival to the track, not ahead of time. If we want to camp together we will need to designate someone to arrive early and reserve a block of sites together. If we organize and get our fees to the designated person ahead of time I think we can succeed in having our group(s) together again this year. Anybody have any other suggestions or is there another plan already happening??
Ron in Cleveland
Admin
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Been a while.

Post by Admin »

You all probably forgot who I am as I havent posted for over a year. My 75 GT750 project was on hold for that time but am now getting her finished for Mid-Ohio next month. (Been beefing up my Buell!) Hope to be able to show my Buffalo off when I see you guys there.

Question: Can anyone suggest a decent, cheap, solid state regulator/rectifier to replace the old clunker?? Thanks

Ron in Cleveland
aka pastorron
Admin
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Post by Admin »

Ron,

Have you tried these guys in Oregon? They list a unit for the GT triples

http://www.oregonmotorcycleparts.com/vregulators.html
Admin
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Post by Admin »

desmocat wrote:FYI, I checked out Ralph Hudson's TR500 and he's using a KR164 on rear and a KR124A on front.

I'm thinking of going to this combo to get some more ground clearance. On of the problems I'm having is grounding out the chambers when cornering, especially on the right side. This certainly limits the lean angle, 'cause when hard parts start touching the ground.....
Does anyone know if the Dunlop KR164 tire fits on a stock 500 swing arm and 530 chain setup? I just purchased this back tire from RCB thinking it would be ok, but now that I have the tire it sure does look wide compared to stock. I'm mounting it on a 2.75 rim. Any help would be appreciated...thanks
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Post by Admin »

CJF wrote: Does anyone know if the Dunlop KR164 tire fits on a stock 500 swing arm and 530 chain setup?
The KR164 won't fit stock swingarm and 530 chain, it's too wide and will rub on chain. I now use the KR164 and went to 520 chain which gives .125" greater clearance. I space the rear sprocket with a .125 thick spacer to move sprocket outboard, then add I think three locking tab washers to front sprocket to move a corresponding amount.
Admin
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Post by Admin »

Thanks for the info Ralph, I had a feeling that would be the case. Can you tell me how you went about making up the rear wheel spacer?
Admin
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Post by Admin »

I used .125 thick aluminum and machined it to fit sprocket ID, Sprocket carrier OD, and 6 hole pattern.
Admin
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Post by Admin »

I don't have access to a waterjet or anything like that, so I guess I'll have to try it out with the old jig saw, drill and sander and see what I come up with.
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Post by Admin »

CJF wrote:I don't have access to a waterjet or anything like that, so I guess I'll have to try it out with the old jig saw, drill and sander and see what I come up with.
Chris,

Get some inch wide 1/8" (.125) thick aluminum strips from a good hobby shop, Home Depot, Lowes, www.mcmaster.com, or www.aircraftspruce.com. A 13/32 drill bit from the same guys (or a 10mm drill bit from Mcmaster if you're being precise). Make yourself a set of washers/square plates to fit behind the sprocket and you should be just fine.

Then again some steel shims from McMaster would be a faster, easier way to go. You could get 3/8 ID shims and open them up with a 10mm or 13/32" bit:

McMaster part number 3088A511

Or some 1/2" ID shims which have a larger than needed ID but should still work pinned between the sprocket and the carrier.

McMaster part number 3088A512

Hope this helps!

Jim
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Post by Admin »

Thanks for the tips Jim. Are you saying to cut the strips so that they cover the full sprocket carrier surface, but just have it in a few pieces rather than 1 piece?
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