TZR500 Race bike

[pstamper]

I am by no way as technical as you guys, but thinking the clearance was OK by feel and eye measurement does not sound right. Calipers are pretty cheap compared to this damage. What are the scratches on top of the piston. Is the piston ring pin still intact. Looks like an expensive build to not take it apart and find out what is really going on. Was the picture of the tap before or after the ring trying to seize? If before where did all the little shaving go. Heck with the gasket even if custom made. Looks like the rest of the engine is custom. Never seen the inside of a TZ cylinder. Not much surface area for the ring. How many hours of operation is the engine good for? Was this a play toy or track bike. If track bike I would definitely take it apart and investigate. Better it happened initially than a real seizure and lock up in the middle of a high speed corner. For both your safety, and if on the track, the safety of others. I would find out what is going on.

[Rick Lance]

[Rick Lance]

[WVWRZ500N]

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[WVWRZ500N]

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[WVWRZ500N]

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[Helmers58]

Hi guys!

I did not have plans to rip of the cylinder today, but you leave me with no choice The piston in the forward cylinders are standard tz4dp, B version which has a dimention of 55.940-55.945mm.

The exhaust valve assy was soaked in oil, so lubrication is for sure not a problem.

When it comes to seizure, I'm not an expert, since I have barely experienced it.

Attached, you'll see pictures of piston, cylinder and ring. Ring opening at tdc is 0.40mm. Cylinder clearance using a feeler gauge is app 0.030 at top' and 0.015mm at bottom when piston is at app top. The piston has also enough clearance to pass through the cylinder. A lot of pictures, but I need to find the cause of the wear marks.

Piston has only light wear at lower skirt on inlet side. Ring has no unusual wear as far as I can see. Head has no "new" marks.

Actually, I was not aware of how important it is to warm up this engine slowly. I have tryed to be carefull with revving before engine reaches 50 degrees, but I might have done it..

I will also remind you guys of the intention of this forum. We all have different meanings, but let's discuss it at a friendly level. Period!








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[WVWRZ500N]

Hi guys!

I did not have plans to rip of the cylinder today, but you leave me with no choice The piston in the forward cylinders are standard tz4dp, B version which has a dimention of 55.940-55.945mm.

The exhaust valve assy was soaked in oil, so lubrication is for sure not a problem.

When it comes to seizure, I'm not an expert, since I have barely experienced it.

Attached, you'll see pictures of piston, cylinder and ring. Ring opening at tdc is 0.40mm. Cylinder clearance using a feeler gauge is app 0.030 at top' and 0.015mm at bottom when piston is at app top. The piston has also enough clearance to pass through the cylinder. A lot of pictures, but I need to find the cause of the wear marks.

Piston has only light wear at lower skirt on inlet side. Ring has no unusual wear as far as I can see. Head has no "new" marks.

Actually, I was not aware of how important it is to warm up this engine slowly. I have tryed to be carefull with revving before engine reaches 50 degrees, but I might have done it..

I will also remind you guys of the intention of this forum. We all have different meanings, but let's discuss it at a friendly level. Period!

Henrick,

Based on your measurements with the feeler gauge the base of the piston has .015mm which is .0005" or half a thousanth of and inch. You should be in the .00275 - .00325" range which is .0.06985 - .08255mm. You should have the piston and bore measured with proper bore gauge and mircometer to get exact measurements before proceeding with running the bike. You should have all four cylinders and pistons measured to make note off all tolerances. You could be in for serious seizure if you don't get this sorted.

Is the ring you are using the one for this piston or a different TZ model?

Regards,
Bill Wilson
Wilson Performance
Lee's Summit, MO
http://www.wilsonperformance.net" onclick="window.open(this.href);return false;
Member RZ500 Owners Group #573
816-377-3185
WVWRZ500N@aol.com

[Andrew]

High performance 2-T's have smaller tolerances so need carefull warming up before being thrashed!
Did it simply get too hot too quick so the piston expanded quicker than the barrel.

[Dubsey]

In one of your comments you say you didn't realise the importance of warming slowly
If the engine is fresh then the tolerances would be even tighter
It looks as if that piston has had a seizure but possibly the others firing have allowed the engine to continue running
As Andrew says it may just be a little too hot to quickly ?
Still a stunning engine

[Helmers58]

Hi!

Thanks for you`re reply. I`ll see if I can borrow some proper tools for correct measurements. I might have misread the feeler gauge readings.. However, the cylinders and pistons are standard tz parts, so I can`t quite see what I have done wrong. The ring had no sign of unusual wear, so I suspect the wear marks in cylinder and at pistons comes from too fast warm up.

Thanks for all you`re help! I`m amazed by all the know-how people in this forum have

[Rick Lance]

The TZ250 4DP pistons (as well as many other pistons for Nikasil cylinder applications) come in a range of sizes designated by letters A-B-C-D with A being standard and each step up typically being 0.0015" or 0.038mm oversize. Evidently your TZ barrels are in near new condition and you have selected a piston that is oversize. Be aware that the standard A size pistons may not be available at this late stage in the 4DP service life since most parts in service have worn past standard bore. You may want to acquire a suitable stock of pistons you are sure will work for you before altering the cylinder bore diameter and limiting options for the future. I would expect clearance requirements to be tighter than iron bore motors and would be comfortable with 0.002" since the alloy cylinder will more closely match the piston expansion. You may wish to work with a company that offers Nikasil plating service to have your cylinders honed since it is nearly impossible to expand the bore size 1.5 thou without serious power equipment dedicated to the task. Hand held hones may also introduce taper to the bore.

[BRIAN TURFREY]

Don't think i would worry to much about the clearance problem that you think you have there. You got plenty of clearance on the blades. If the piston was to tight on clearance , you will see what we call stick marks on the four corners of the piston. What,,, piston is round right? Yep, what we refer to the corners is the part of the piston, inside that has the ribbing or thicker material ribs. When the piston is hot, the thicker parts stay bigger in size than the smaller parts. You don't have stick marks on the corners. Think you will find the problem you have there is water getting into the cylinder. Looking at the pictures of your cylinders,, top of that one cylinder is a fu...king mess and needs to be put on the surface plate and lapped. You can clearly see the sand blast areas. What are the heads like? The marks in the cylinder are the same as on the single cylinder dyno test engine we had at Team Roberts shop. When i was in to much of a hurry or the phone would ring, some times i forgot to tighten down all the head bolts. After we ran it, the cylinder would always have them same marks. Water would leak in There is one thing that I do agree with,,, Mr Rick Lance,,, "oh shit, look out,, here we go",,, think he is correct when he said there is a fine ring impression on the top of the piston in that one picture as if the piston did tap the head. You can clearly see that. Well done Mr Lance. Good eye sir!!. So, think what i would do is lap cylinders and heads,,, new std TZ 250 head o-rings. Check all the threads in the cylinders. Run it. Good Luck.

[Helmers58]

Hi Brian!

Thanks for the advice. Don`t know if you read it, but bad threads in cylinder and a leaking head was actually the reason for discovering the wear marks. Regarding the piston, the circle pattern may have been present before assembly, since the pistons where used. The engine has only been running for like 20 minutes or so.. The squish is between 0,6-0,7mm.

Thanks again for the advice. I hope I`m ready for dyno soon! Will be a lot of work, since the carbs are dellorto VHSB, and needs to be adjusted a lot!

By the way, hope all of you guys have seen this bike

http://www.ronax500.com/en/index.php" onclick="window.open(this.href);return false;

I will see if I can resurface the cylinder top before installation. The head looks better

[jante350]

Have a look here, although nothing exactly like that, but it does suggest to tight clearance.

http://www.smellofdeath.com/lloydy/pist ... _guide.htm" onclick="window.open(this.href);return false;