Run or Replace - What Do You Think?

CR500PHIL · Post by **CR500PHIL** » May 14th, 2011, 11:40 am

Here are a couple pics of the piston from my 500. There is obvious worn ring issues. My question is would you replace this piston or just rering? The cylinder looks great - no scoring at all.

2strokekyle · Post by **2strokekyle** » May 14th, 2011, 11:52 am

Piston looks usable, but what is more important is what it measures compared to the bore.

iggys-amsoil · Post by **iggys-amsoil** » May 14th, 2011, 11:54 am

I need a bigger monitor.

Measure the cylinder and piston, only way to know fer sure.

CR500PHIL · Post by **CR500PHIL** » May 14th, 2011, 12:03 pm

iggys-amsoil wrote:I need a bigger monitor.

Measure the cylinder and piston, only way to know fer sure.

I left the images large to show detail - my monitor is 46" though. LOL

Post by **AlisoBob** » May 14th, 2011, 12:59 pm

What are you using for filter oil?

Wesson?

I'd start over.

CR500PHIL · Post by **CR500PHIL** » May 14th, 2011, 3:00 pm

AlisoBob wrote:What are you using for filter oil?

Wesson?

I'd start over.

I have not rode this yet - just finished building and done a compression test and then tore it down. It seems there is was a lot of blow by. The cylinder to piston clearance is within spec but on the higher end of spec. The ring end gap is much larger than spec.

Tharrell · Post by **Tharrell** » May 14th, 2011, 4:28 pm

I'd start over too.
I'm not the sharpest knife in the drawer but, the highly specific blowby suggests a problem somewhere.
To me, a new topend is cheaper than a new engine.
I'm getting ready to do it to my 480.

Kuma · Post by **Kuma** » May 14th, 2011, 5:16 pm

blowby looks strange, is that the result of the dreaded stop sign bore?

CR500PHIL · Post by **CR500PHIL** » May 14th, 2011, 5:23 pm

Kuma wrote:blowby looks strange, is that the result of the dreaded stop sign bore?

Not sure - there is blow by on each side of the piston - around the wrist pin area and also some towards the intake / carb area. I measured the bore though and it does not seem off. Tomorrow I am bringing the cylinder to my father's house the cylinder to confirm the bore with better equipment. If it needs a bore I will just sell the bike for $50.00 and a case of beer.

Tharrell · Post by **Tharrell** » May 14th, 2011, 6:08 pm

So, it's 1.00 over?

CR500PHIL · Post by **CR500PHIL** » May 14th, 2011, 6:23 pm

Tharrell wrote:So, it's 1.00 over?

Yes it is so no problem boring. The problem is I live where a good machine shop is hard to find - may need to send it away for a good bore job else risk letting the local yahoos play with my cylinder. Ironically I just got back from Boston - should have taken it with me and had it done there.

Gmbond · Post by **Gmbond** » May 14th, 2011, 8:05 pm

Shipping within Canada sucks! Overpriced an slow!

That said for someone who seems to have a grasp of what's needed to be done right on these, Roosty seems to be the guy if you need to ship it anyways.
I went local and am happy with my results so far, but if I didn't have someone nearby I trusted it would have gone to Millar (Roosty) if for no reason than he seems committed to the cr500 for the past and future

2strokeforever · Post by **2strokeforever** » May 14th, 2011, 10:46 pm

Roosty seems to be the guy if you need to ship it anyways

roosty delivers far better than oem work

CR500PHIL · Post by **CR500PHIL** » May 15th, 2011, 4:44 am

2strokeforever wrote:
Roosty seems to be the guy if you need to ship it anyways
roosty delivers far better than oem work

I PMed Roosty about it.

CR500PHIL · Post by **CR500PHIL** » May 20th, 2011, 8:36 am

Bore was within spec in terms of being round so I cross hatched it and ordered a new complete Vertex top end. I cannot wait to try this beast with a new top end. The old piston will be a pen holder at work. :-)

Tharrell · Post by **Tharrell** » May 20th, 2011, 10:52 am

Did you get a compression reading on the old top end?

CR500PHIL · Post by **CR500PHIL** » May 21st, 2011, 9:16 am

Yes it was 60 - the ring end gap was over 1mm - rings were toast. The moron I bought it from on eBay said it was just rebuilt but thankfully all it needs is top end or so it seems. It has a brand new right side cover / water pump which is great since it is the MG one.

Tharrell · Post by **Tharrell** » May 21st, 2011, 9:53 am

Well, that's the blowby explanation.
I can hardly believe it ran at 60psi!
I would certainly replace the whole top end if it were me.
But then, I would probably redo the crank just to be sure as well.
If you caught Doggers rebuild thread, that's about how bad I have it.
It's a very informative build as well as the others on here.
Good luck and keep us informed. Tony

CR500PHIL · Post by **CR500PHIL** » May 22nd, 2011, 6:57 pm

I had it started once but man was it hard to get going - I knew at that point something was wrong. I am waiting for the parts to come now. The crank checks out fine as far as the tests I have done. We have a short summer here and I really want to get this thing running. This winter I think I may split cases etc and I have a few upgrades I want to do - ex. newer style wayer pump cover to replace the MG one.

CR500PHIL · Post by **CR500PHIL** » May 31st, 2011, 6:14 pm

I installed a complete new Vertex top end tonight. I started late so I have to finish tomorrow evening. I cannot wait to try this bike - I even took Friday off to tune the bike in.

Tharrell · Post by **Tharrell** » June 1st, 2011, 3:35 am

What are the clearances?
What about the crank seals?
A compression and leak down test would be great after the rebuild too.

CR500PHIL · Post by **CR500PHIL** » June 1st, 2011, 5:34 am

Tharrell wrote:What are the clearances?
What about the crank seals?
A compression and leak down test would be great after the rebuild too.

Piston to cylinder clearance is fine - top end feels much tighter - I think the wrist pin bearing was really worn. I will perform tests once the engine is fully assembled - hopefully tonight but never can tell when you have four year old twins in your care.

Tharrell · Post by **Tharrell** » June 1st, 2011, 9:02 am

4 year old twins?

How do you get ANYTHING done?

Post by **MojoScojo** » June 1st, 2011, 9:03 am

Tharrell wrote:4 year old twins?
How do you get ANYTHING done?

x491

CR500PHIL · Post by **CR500PHIL** » June 1st, 2011, 6:13 pm

MojoScojo wrote:
Tharrell wrote:4 year old twins?
How do you get ANYTHING done?
x491

I got to say I enlist a little help from Budweiser at times.

BannedCR500Riders.com

Run or Replace - What Do You Think?

Run or Replace - What Do You Think?

Piston

Piston

Piston

Bore

Bore

Bore

Compression

Rebuild

Re: Rebuild

Twins