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#1 |
Veteran
Join Date: Dec 2015
Location: San Jose, CA
Motorcycles: KTM/Triumph/GSXR
Name: Mario
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Opinion on rebuilding KTM engine
My KTM 500 sumo is due for a rebuild, running it at the track has not been nice to the engine and I'm getting 10% leak and hard to start. ~120hrs 2,200mi
I am considering two options: 1) tear down and rebuild myself: i would send the head/valves and cylinder out to a shop, I'd just slap everything together with a new OEM piston, rings, bearings, etc 2) send complete engine to a local shop and ride dirty bikes while I wait I am good at wrenching and reading manuals but never done an engine rebuild. On the other hand, I do not know of any local shop that I can send my engine to. Can anyone comment on 1)? If you send the head and cylinder out, do you still need special skills/tools to disassemble and assemble the engine? Regarding 2), anyone know of a really good and reliable shop that can quote an engine rebuild? I don't need race stuff. I don't think I''ll be taking the sumo to the big tracks ever again. Thanks! ![]() |
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#2 |
2fast 2live 2young 2die
Join Date: Mar 2003
Location: Truckee & SF
Motorcycles: All of them eventually.
Name: nope
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A top end is not hard to do by yourself, if you have the time, tools, patience, wrenching experience and a service manual.
Engine Dynamics in petaluma can get the cylinder and head ready to drop back in. 1) no "special" tools needed, at least not readily available ones. Just a good metric toolset. 3) locally or ship to? Thumper racing, off the top of my head Last edited by augustiron; 10-19-2018 at 12:00 PM.. |
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#3 |
re-tarded
Contributor + 3%
Join Date: Aug 2006
Location: Alameda
Motorcycles: SV1000,WR450tards(03FS), YZ426tard,NC700X
Name: Daniel
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I'd look into how long the bottom ends on those tend to last.
If you think the crank is probably in good shape, it isn't hard to do a top end (especially if you have a shop cut the head for the new valves). I'd expect that to have a nikasil cylinder and therefore you shouldn't need to send the jug out, but I could be wrong. |
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#4 | |
Darwin's exception
Founding Member
Barfie Winner 2017
Contributor ++++
Join Date: Feb 2002
Location: San Francisco and Lake County
Motorcycles: Triumph Street Triple, YZ250, TLR200, XR400R, Husqvarna CR390, ST1100 and couple more...
Name: CJ
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Quote:
Other than the plethora of torx bolts on the engine, the KTMs are pretty straight forward. Some aspects almost easier to work on then other brands. Split and reassembled a 350 recently. Until you open it up, it will be tough to say what you need to replace or even give and accurate quote. But your leakdown test can give you some clues. Attach it again, but pull off your valve cover, your airbox boot and filter as well as your oil fill plug on the engine. Pressurize again, but this time listen for where air is escaping. Coming out the end of your exhaust (exhaust valves) out your airbox (intake valves) out your oil filler hole (rings). Not definitive, but get you started. ![]()
__________________
I'm looking for 1970 or older project like a CB350 or Triumph 650. Cheap and complete. PM me if you have something - will provide it a good home. ![]() If you think me being naked is offensive, dont look! ![]() "You find the biggest meanest bull, chop off his balls, dangle them in front of him, then hop on his back. That should give you some reference point. Either that, or shove a shuttle rocket up your ass. Take your pick." Colin Edwards 'Cycles is a mean toy lady" Big Halsy |
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#5 |
poseur
AMA #: 1093637
BARF Moderator
Founding Member
BARFie winner 2014 & 2017
Contributor ++
Barf Dirtbike Political Advocate
Join Date: Apr 2002
Location: San Jose, bottom of dirty 130
Motorcycles: ‘18 Alta EX006, ‘17 Alta MX019, 06R6, 05TM503 Black Dream, 01TM250 2T, 91ATK406
Name: Butch
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Ah, just buy an Alta. I hear they are having a big liquidation sale.
Sorry. Couldn’t resist.
__________________
Butch Hodaka Ace 90. I've been riding these things too long. What can I say? How about that Combat Wombat? Terms of Service: http://www.bayarearidersforum.com/info/tos.php and get a dirtbike! preferably a 2 stroke... Or... Electric! |
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#6 |
Veteran
Join Date: Dec 2015
Location: San Jose, CA
Motorcycles: KTM/Triumph/GSXR
Name: Mario
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Thanks for the feedback, I'll give it a try to rebuild myself.
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#7 |
Darwin's exception
Founding Member
Barfie Winner 2017
Contributor ++++
Join Date: Feb 2002
Location: San Francisco and Lake County
Motorcycles: Triumph Street Triple, YZ250, TLR200, XR400R, Husqvarna CR390, ST1100 and couple more...
Name: CJ
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Their shop manual is really well written and easy to follow other than calling bolts screws in the translation.
![]() The toughest part of the KTM top end job will be installing the piston oil scraper and rings. ![]() ![]() You will also find the KTM OEM pistons and rings are ridiculously priced compared to other bikes. Use the OEM gaskets and then get yourself a aftermarket Vertex piston and rings. The KTMs are pretty easy to work on. Good luck ![]() edit: and pay attention to piston orientation. The manual on the 350 we just did says the mark "A" piston top goes forward, where the on the Vertex piston it was just the opposite. Pretty easy to see if you pay attention to the valve sizes and the corresponding cut outs on the piston. ![]()
__________________
I'm looking for 1970 or older project like a CB350 or Triumph 650. Cheap and complete. PM me if you have something - will provide it a good home. ![]() If you think me being naked is offensive, dont look! ![]() "You find the biggest meanest bull, chop off his balls, dangle them in front of him, then hop on his back. That should give you some reference point. Either that, or shove a shuttle rocket up your ass. Take your pick." Colin Edwards 'Cycles is a mean toy lady" Big Halsy Last edited by OaklandF4i; 10-21-2018 at 07:04 PM.. |
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#8 |
Veteran
Join Date: Dec 2015
Location: San Jose, CA
Motorcycles: KTM/Triumph/GSXR
Name: Mario
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Cool, thanks!
This might be a stupid question, haven't googled this yet... what's the process to pick a piston size? have it measured, machined/re-honed to a certain diameter that fits the closest piston within tolerance? Edit: time to educate myself, hope these two are good ![]() Last edited by Mario; 10-21-2018 at 07:36 PM.. |
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#9 |
Veteran
Join Date: Dec 2015
Location: San Jose, CA
Motorcycles: KTM/Triumph/GSXR
Name: Mario
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#10 | |
Darwin's exception
Founding Member
Barfie Winner 2017
Contributor ++++
Join Date: Feb 2002
Location: San Francisco and Lake County
Motorcycles: Triumph Street Triple, YZ250, TLR200, XR400R, Husqvarna CR390, ST1100 and couple more...
Name: CJ
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Quote:
You will inspect and measure the cylinder or take to a machine shop to do it for you. Some cylinders wear (ie enlarge slightly) and are still usable. Then you order one of the slightly larger pistons available, size is based on your cylinder and the specified piston to cylinder gap in the manual. That said, I almost always use the standard piston size on my bikes and just replate when worn. If you keep track on the time/wear/condition of your motor, you should be able to get multiple top ends off the original plated cylinder. Wait too long, and you risk wearing them out like anything else. Some brands, like Yamaha two strokes have oem matched pistons to cylinders based on the stamping like A, B, C etc on the cylinder's outside wall. Even then, I just use the standard aftermarket piston. I'm not a pro or looking for the last .001% of HP. I try to use OEM when affordable and almost always keep to stock compression for reliability, longevity, and fuel (higher compression tends to be more finicky with knock, heat, fuels, etc.) I'm not a professional wrench or rider, but thats what has worked for me for years. Will always defer to a Pro. Others experiences may vary. ![]()
__________________
I'm looking for 1970 or older project like a CB350 or Triumph 650. Cheap and complete. PM me if you have something - will provide it a good home. ![]() If you think me being naked is offensive, dont look! ![]() "You find the biggest meanest bull, chop off his balls, dangle them in front of him, then hop on his back. That should give you some reference point. Either that, or shove a shuttle rocket up your ass. Take your pick." Colin Edwards 'Cycles is a mean toy lady" Big Halsy |
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#11 |
Veteran
Join Date: Dec 2015
Location: San Jose, CA
Motorcycles: KTM/Triumph/GSXR
Name: Mario
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That's some great feedback!
![]() I'm now leaning towards doing it myself (minus head and measuring of cylinder). The more I learn about these machines, the better I get at keeping up with them ![]() |
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#12 |
2fast 2live 2young 2die
Join Date: Mar 2003
Location: Truckee & SF
Motorcycles: All of them eventually.
Name: nope
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Take the head, cylinder and piston to engine Dynamics in Petaluma. They will redo the head in its entirety and check the piston and cylinder for you and advise if you need to overbore, replate, etc. Odds are a hone and rings will be all you need unless there is scoring.
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#13 | |
Veteran
Mod Alumni
Founding Member
Top Percent Poster
Contributor +++++++++
++++++++++++++3%
Join Date: Sep 2002
Location: Oaklamd
Motorcycles: Yamasuzhonaki 1450
Name: Beelzebub
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Quote:
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That's not true! The lie is actually the truth! I know. Lots of people know this. |
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#14 |
Veteran
Join Date: Dec 2015
Location: San Jose, CA
Motorcycles: KTM/Triumph/GSXR
Name: Mario
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Engine Dynamics it is! Once the rain season starts, the engine comes off and to Petaluma. Thanks all for the feedback!
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#15 | |
Veteran
Contributor
Join Date: May 2012
Location: Sonoma County
Motorcycles: XR-400 (plated), RM-250,
R1150RT
Name: Tom
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Quote:
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Tom |
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