Bottom and top case matched on T500?

[Repeater]

I broke the oil drain bolt housing on the bottom of my T500. I want to replace the bottom case when I do rebuild the crank. It smokes like a mofo from the clutch side pipe and not the throttle side. Still runs and has a nice tan to the plugs.


Are the cases matched to each other or would I be ok just replacing the bottom. I want to keep the top case with the right numbers. Worst case I'll take the bottom case to a machinest and have something welded up. I'm using a rubber pulg that works but has a slow drip.

What have you spent to rebuild your engine. Crank seals, pistons, etc. Never done it before. Any step by step threads on this and what is needed?

Thanks.




D

[Coyote]

$$$$$$$$

[parksie]

I believe that the cases for the 500s are matched and should not be mixed, however Muzza in WA says that he has mixed them several times with no problem.

[titan performance]

Never had cause to do it.....but with mass produced Jap stuff, I'd mix them to be honest.

[Vintageman]

If I have the crank out I like to change Con rod, Con Rod Crank Pin, Big End (BE) Needle Bearing minimum. The main crank Roller bearing (outer two) you can inspect with your eye seal out.

Con rod not always available. on my T500 it took me two years to find and now very rare. There is the Cruzinimage experience for these obsolete parts I can’t verify ok but be cautious and check them for tolerances for example.

You don't have to change rod. Look at small end rod eye for deep rust stain stripes caused by small end needle bearing or pitting now.

The side to side rocking test is good way to know if OK. And if in spec, you change crank pin and BE bearing, it gets much better after usually.

the t500 BE cage is obsolete. You can use gt750 BE, but up cross until you see the one for rmx250 if i recall. bill bune has these i think in stock. bill bune does ok and experienced but at that price they get the actual work done in short. i don't wait for him to tell me if i need crank pin for example . I just buy and tell him to put in. he gives your old ones back and they always so far show some wear or environmental affects.


enough for now… got to go

[johnakay]

didn't Cruzinimage didled one of our members out of 5 grand to make these conrods?

[argo1974]

T500 engine cases are marked as a pair by factory. There are 2 chisel marks on the cases behind front sprocket.

[tz375]

On a bike like a TZ350 which revs high all the time, we typically replace rods pins and big end bearings. On a slow revving street bike, the loads are significantly lower and it is rarely necessary to replace pins, mains or rods unless they show a lot of pitting or wear.

When a crank does have badly worn/rusty parts it is usually possible to strip a second crank for donor parts. That is why some of us will buy cranks if they are cheap enough - just to be there as possible donors.

If your crank is really bad, new bearings and rods might be a better path to longevity but it comes down to cost and availability.

Not that I recommend this but I know a drag race team that took a used crank and used for a couple of years without changing anything on the crank. No seals bearings or rods were replaced until a piston melted down and filled the bottom end with metal.

[Vintageman]

OK you have slightly different advice on bottom end... what to do with all this info is up to you

Let's talk top end. I’ll start it off

If the engine is running now how quiet is the top end while running idling at 1500 -2000 rpm?
Is it noisy, rattling, scuffing or slapping? If not your top end may be fine. It gets no better than a quite smooth running top end.

Check compression. See how well balanced the two side are. Once you take the top end off keep everything together. Check the cylinder liner top for a ridge. This is where the top rings stops at its highest point. You may have some carbon and rust above that point so you need to clean up to see if a true ridge. When I say ridge I mean wear in the actual metal of the liner. If there is distinct ridge you can see of feel , cylinder is worn. Check around ports at middle area look for wotn concave areas or lips. Hold to sun light and these areas will reflect light differently.

Your cylinder will always have some wear versus new but if little I let it go especially if it is running smooth, quiet and even compression as explained.

There are tools do this per the book (measure wear like a pro or pros) but your eye can tell you a lot. If the cylinders and piston don’t have significant signs of scuffing you may be able to reuse. And, it's already fitted in well. Not often do I find them like this but I do and enjoy.

Check the rings for gap too large cylinder worn and/or rings warn. It can be just rings more so than lines but if you change just rings (very common low buck method)) you will have to deglaze liner (skip down to that below)

A little fine scratches about the ports, I would not worry. A top end is an easy job to do later. In this rare but plausible case liner OK I just clean up carbon and put back together as it was. I don’t not touch cylinders and leave them as is with their wonderful slipper oil glazed liners.

I will alway renew wrist pin, wrist pin bearing and clip

Now the piston. If the tops looks like it is starting to decay/erode/ you have to replace. At this point I'll change rings too. If I feel the liners are in spec I'll go standard size. I use a cleanup brush or ball hone to deglaze the nice oil film off liner just so new rings will seat, that's it. Go no deeper. Don't try to remove all the scratched for all you have done is make is a larger clearance and that results in the quiet top end being noisy due to added piston slap top end noise. On air cooled engine it is sensitive and you will learn to dislike that sound amplified by the cooling fines and vibrations in you body as you ride. Going standard size new piston you are not trying to make cylinders like new. That’s next

If there is too much wear ,over sizing the bore to match a new piston set is advised. My most common choice, but it is not without risk (analogous to a surgeon performing an operation). Talk to your machinist of choice and discuss what he/she uses for equipment and how they do the process in steps. Tell them it is important to you that it fits per spec. Anyone with proper tools can do a good job. It is just not automatic (some new hone machine are more so today, but who has?) and requires the operator to take their time and measure a few times as they get near then end.

Next is carburetor!