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WS7II Rebuild

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M

madnking

Gone - bye bye.
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I bought a WS7II last may and ran about 4-5 gallons of fuel through it while I had tuned it on the lean side(250-285). It ran awesome all year and I was cleaning it to prepare to store it for the winter and when I removed the piston the top was pretty black. I clead it to a brown but it still looks bad. It ran fine at the end of the year absolutely no problems, but should I rebuild for next year? I don't want to have any problems next race season if I can help it. Also when do the bearings start to go bad and is it worth replacing them? A piston and sleeve for a WS7II is kinda expensive maybe when it comes time I should just buy a new one?thnks
 
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madnking said:
I bought a WS7II last may and ran about 4-5 gallons of fuel through it while I had tuned it on the lean side(250-285). It ran awesome all year and I was cleaning it to prepare to store it for the winter and when I removed the piston the top was pretty black. I clead it to a brown but it still looks bad. It ran fine at the end of the year absolutely no problems, but should I rebuild for next year? I don't want to have any problems next race season if I can help it. Also when do the bearings start to go bad and is it worth replacing them? A piston and sleeve for a WS7II is kinda expensive maybe when it comes time I should just buy a new one?thnks
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mines black on top as well and still going strong
dont know about you guys but we buy them for about 650nzd and it cost about 450nzd to rebuild them and theres no gaurantee that it will be as good as a new motor once rebuilt, i tend just to throw them and start again, i would just run it, bet you get a fare bit more use outta it yet colour of piston is not really an issue it more wehter its got scoring or pitting, conrod has no play and bearings are still in good nic :)
 
THnks Mike I can get a new for $304 and it looks like a piston and sleeve will run me $117. I prob should replace the rod as well so I'm prob. over $160 so I guess I just get new and have a backup. Have you had any exp. with resizing? Its only $20. thnks
 
I've seen a few resized p/s and they all ran awsome. They were done by os rocket on ebay. From what I saw they ran better then new!
 
Clean the top of the piston with RB oil and white paper towels the best you can, put it back together and run it.

the black is just from it being a bit lean. It doesn't really hurt the engine, but it will fowl out glow plugs faster when some of that black junk releases while running.

the rb's are pretty damn tough engines. When rand at modest levels (230-250) the last for a long time.

I don't personally rebuild them or recomend having them pinched. They always seem to break the rod shortly after being pinched.

also, one tip for reassembly. Make sure the piston is at top dead center before you put the butt plate back on.

Brandon
 
madnking, the engine will tell you when it's done, not what it looks like on the inside. The tell-tell sign of a hosed engine is a flame out that can't be fixed. If it just starts flaming and especially if it's hard to start when warm, it's toast. Don't listen to the pinch tests and the compression tests and the flop test. It's all in how it runs.

As far as a rebuild goes, a lot of stuff gets hammered in an engine over time. Sure you can replace the piston, sleeve and the the bearings, but in the end you just spent more than yuo would have on a new engine.

The pinch thing has yet to work for me. Now, don't take that as me saying it sucks or it doesn't work. I think I just messed up. First, don't send it in too early. If it's not flaming out, don't send it. Second, follow those instructions OS Rocket gives you to the T and if you are confused email him. Last but not least, change the conrod after you do the break-in again. That's very very important.

EDIT: One last thing on getting a pinch. I've heard of people getting a "light" pinch. My pinch was too hard. I don't know if it was because I sent it in too early or if I just cause I didn't ask for a "light pinch". Maybe email OS Rocket or something and ask when it's best to send it in and when one should ask for a "light pinch". You surely don't want the same experience I had. :(

Anyway, good luck with it.
 
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