RGV250: Engine removal, Strip and rebuild

[MarJay]

Hello,

As many of you know, last year I did a few trackdays on my RGV. Indeed, some of you were there when my bike decided it only wanted to run on one cylinder on the last lap of the last session of the day.

https://www.bikechatforums.com/files/rgvcad6.jpg

Some of you even helped me take the bike apart in a vain attempt at a diagnosis! For that I am grateful. (keith! )

The consensus for the past six months while the bike has sat in my garage, has been that it was the big end bearing on the top cylinder. This conclusion was reached after seeing the impact the piston had with the spark plug, and the state of the piston crown. When I removed the head, I found no movement of the piston which would indicate little end failure, and the crank turns over and the bike runs (albeit very noisily) which would seem to preclude the main bearing failure.

Fast forward to Easter weekend. I resolved to do some trackdays this year, so decided I would need a trackbike. This meant getting the RGV working again, so I began to strip the bike for the purpose of dropping the engine. A few minor distractions aside, I completed the process last Sunday.

https://www.bikechatforums.com/download.php?id=46556

I decided to strip the top end of the engine, so that I could really see what was going on inside the motor. I fully expected knackered big end bearings... but they were fine.

https://www.bikechatforums.com/download.php?id=46555

The problem seemed to be confined to the piston, as you can see, it has very worn rings and quite a bit of crown damage...

https://www.bikechatforums.com/download.php?id=46554

The piston on the right in this pic is the first thing I saw when I got the top cylinder barrel off of the bike:

https://www.bikechatforums.com/download.php?id=46553

Somehow the skirt has shattered!
I've looked this up on the web, and apparently the skirt can shatter if the bore is worn and the piston rattles up and down the bore. However despite the excessive damage to the piston, the bore seems in good condition:

https://www.bikechatforums.com/download.php?id=46552

And the bottom cylinder:

https://www.bikechatforums.com/download.php?id=46551

I have taken the engine to a trusted local mechanic, who tested the new pistons in both sets of barrels (the ones from my engine, and the ones from an aprilia RS250 engine that I bought) and he said that the Suzuki ones were in better condition, and that he would strip and clean the powervalves. He is going to get the crank out on Saturday and have a look and give me a price on a rebuild. Now that I know that the big end is OK, I'm hoping that the bit of piston that dropped into the crankcase hasn't done too much damage, and that with a quick flush out (and perhaps some replacement main bearings) the engine will be ready to rock and roll.

If the crank needs any work then I'll leave it to him, but otherwise I plan to rebuild the top end myself.

Look Ma! No engine:

https://www.bikechatforums.com/download.php?id=46550

Assorted RGV Bodywork and other bikes:

https://www.bikechatforums.com/download.php?id=46549

My tarty nikon expansion chambers will also need some work, as they have a bit of surface rust (where it pissed it down on the trackday and I put the bike away wet). I'm semi planning to get some BBQ paint and give them a once over, but it might destroy the tarty beauty of the raw steel and welds. Mind you, they are so rusty now anyway I don't think it will matter. I'll have to dig out some wire wool and buy a family pack of coke! Maybe sainsbury's economy cola will have the same effect for less cash.

https://www.bikechatforums.com/download.php?id=46548

I will also need to replace the end can gaskets. I really really ought to re-pack the end cans too, as they are noisy as hell and my MOT tester said he would chuck a a bucket of water over me if he saw me near his house with it! Somehow it did pass however... Which reminds me. The MOT is due on the 12th of may .

I'll have to get it all roadworthy soon anyway because I'll need to run in the new pistons. RGV250.co.uk reckon 50 miles should do the job. 50 miles of roundabouts and dual cabbageway and not in town I hope! My wrists would never forgive me, and the clutch would be into its final death rattle!

Anyway, watch this space for further updates on MarJays Latest Project:

Operation Get RGV250 trackworthy before snetterton on the 24th of May!

It has a nice ring to it don't you think?
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[cqueen]

Interesting! good luck

[Deano]

good luck marjay. probably running on one cylinder due to no compression.
personally if i had more time i would of taken the bottem end apart myself.

when you've rebuilt one engine. you know its nothing to be scared off. the only thing i worry about with my engine rebuild was the cam timing.

[MarJay]

[Gazdaman]

That sounds like a result to be honest mate. Might mean splitting the cases to find the bit of piston and to check for damage. But at least it shouldn't mean a crank rebuild or new crank...

When I took the head and barrel off the MZ the bottom piston ring was missing a massive chunk, never found the chunk either.

Gaz