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Hey guys,
I've recently torn down my 07 wee due to some insane oil consumption. It has lived a fun life, with lots of aggressive high RPM use. I gotta say I'm really impressed by the reliability of the motor. It has never let me down and so far nothing actually broke. It runs quietly, smoothly, no shifting issues or anything.

The issue is I found myself adding 1 liter of oil per 600 miles. It would stink and puff smoke like no other, so it was time to figure it out. Thought you all would enjoy this.

Upon disassembly:
1. There was a significant amount of carbon built up on the pistons. Enough to fill up the valve recesses and build up about 1mm on the surface.





2. All piston parts fell within spec (piston diameter, bore diameter, piston compression rings, rod bearings, wrist pin, etc). The bore looks fantastic.





3. The cylinder head has seen better days. I've always kept the valves within spec, but one of the exhausts was totally pitted and leaking. The other exhaust and intake valves looked fine. The exhaust valve guides were shot, noticeably loose and allowing the valves to rattle around freely. The intake valve guides were tight still.

I will be replacing the heads with low mileage heads, putting new valve seals, and new piston rings with a fresh hone job. Hopefully it solves the issue and total cost is under $400. I will post up more updates. Long live the wee!
 

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A very interesting post. We don't see many, like that.

Thanks :)
 

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Well done and thanks for posting with pics.
 

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By the looks of things , the piston/ring area was not the contributing factor. Look at the machining on the Piston skirt. Fantastic!
So Class,... What has contributed to the valve guides' early destruction? (fig 3)

Thanks Cobrakai for sharing and caring.
 

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Discussion Starter #6
By the looks of things , the piston/ring area was not the contributing factor. Look at the machining on the Piston skirt. Fantastic!
So Class,... What has contributed to the valve guides' early destruction? (fig 3)

Thanks Cobrakai for sharing and caring.
I'm not even sure I'd call it "early" destruction. 90k HARD miles and the engine still worked, and went fast. I'm impressed!

The one thing I have no spec for is the oil scraper rings. They appear to be very low tension on the cylinder walls. I am interested to see how the new rings fit once they show up.
 

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I did some top end work on a K7 Wee with 80K miles, not as involved as your project. It was burning 1Qt/3000 miles so not as bad as yours. I was going to do the valve seals but sold the bike before I got to it. FYI, I did find exhaust cams were pitted at the apex so you'll want to check that. I replaced them with lower mileage cams from a K9 and even though the K7 cams were still in spec the K9 cams were noticeably "peakier" compared to the rounded K7 cams at 80K miles. The motor seemed to have more power with fresh cams after the work.
 
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I did some top end work on a K7 Wee with 80K miles, not as involved as your project. It was burning 1Qt/3000 miles so not as bad as yours. I was going to do the valve seals but sold the bike before I got to it. FYI, I did find exhaust cams were pitted at the apex so you'll want to check that. I replaced them with lower mileage cams from a K9 and even though the K7 cams were still in spec the K9 cams were noticeably "peakier" compared to the rounded K7 cams at 80K miles. The motor seemed to have more power with fresh cams after the work.

Pink Floyd: And did you exchange a walk-on part in the war for a lead role in a cage?
Welcome to Scamdemic, it gets worse here every day. They pen us up with controla pass, then they tell us we can't play.
 

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Discussion Starter #10
Rings and valves at 90K, color me impressed.

What does a fresh(er) set of heads cost?
I got these for about $100 some years ago when I went to SV cams. Looks like they are going for about $150 now. The nice thing is you can use any SV or Wee heads since they didnt change them for many years other than the dual spark conversion.
 

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I'm not even sure I'd call it "early" destruction. 90k HARD miles and the engine still worked, and went fast. I'm impressed!

The one thing I have no spec for is the oil scraper rings. They appear to be very low tension on the cylinder walls. I am interested to see how the new rings fit once they show up.
My curiosity gets the best of me... The exhaust valve guides are rattly loose, but lateral (cam induced) movement while in operation is curtailed by the bucket that glides in a bore. The piston shows little blow-by but oil char at the 90 degree position. I would like to hear from a Wee strom fleet mechanic (south american police vehicles) to give commentary.) Which head displayed damage? Front or rear. With pitted seat area I would speculate high heat of valve soaking up the stem to degrade the guide and seal.
 

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My curiosity gets the best of me... The exhaust valve guides are rattly loose, but lateral (cam induced) movement while in operation is curtailed by the bucket that glides in a bore. The piston shows little blow-by but oil char at the 90 degree position. I would like to hear from a Wee strom fleet mechanic (south american police vehicles) to give commentary.) Which head displayed damage? Front or rear. With pitted seat area I would speculate high heat of valve soaking up the stem to degrade the guide and seal.
Actually I only have the front cylinder out right now. I'm going to put it back, rotate the engine, and do the rear next. That might tell a very different story. In fact, I hope it has more carnage since it's not totally obvious where my oil is going at this point.
 

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It's good to see a post and photos about repairs to the inside of the motor. A photo of the head and valve guide wear would be instructive.
 
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Did the nearly the same as you. My 05 650 just under 100K was using a lot(Not as much as yours) of oil. Found the cyl. in desent shape with a fair amount of carbon on the piston top, but with blowby that was part of the problem. The valves were another thing. Lateral movement was almost triple the factory specs and the cost of parts alone was to much even without labor, so I found a pair of 12K heads. Those got new seals.
The cyls. could of just got new rings, but I chose a 680 kit just for the heck of it.
Here is the write up on it.
 

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Discussion Starter #15
Did the nearly the same as you. My 05 650 just under 100K was using a lot(Not as much as yours) of oil. Found the cyl. in desent shape with a fair amount of carbon on the piston top, but with blowby that was part of the problem. The valves were another thing. Lateral movement was almost triple the factory specs and the cost of parts alone was to much even without labor, so I found a pair of 12K heads. Those got new seals.
The cyls. could of just got new rings, but I chose a 680 kit just for the heck of it.
Here is the write up on it.
Awesome, I think I stumbled on your old post while researching. I have been thinking about doing this job for a while now since the bike started consuming a noticeable amount of oil around 60k miles. It just never was bad enough until recently. I am planning a long trip and calculated I would need to bring 2 gallons of oil with me to complete the trip 😂

My low mileage heads do have some valve wiggle, but nothing to the extent of the worn out heads. I am curious what kind of play there is on brand new guides. I am guessing .003-.004". The other benefit of the new heads is the valves are in way better shape.
 

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Got the new low mileage head lapped so it has a nice flat surface for the head gasket.

284687


Did some minor lapping on the valve seats using a spare good valve because there was some minor surface rust.
284688


I went with Cometic viton valve seals which popped on nicely.
284689


Cylinder honed with a 240grit SiC Flex Hone.
284690
 
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