Hmmm...A real stumper, for me anyways =)

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#1
I was riding a few days ago at the local sand beds and had been riding for about 20 min when all of a sudden the bike bogged out bad (like i left the gas off or something) and just died. Me and my friend tried to start it for like an hour but it just wouldnt. Everytime we tried to pop start it, it would just back fire really loud and when we changed the plug it didnt help. We took the knew plug out and it was pretty dry and only had a little OIL on it, there was no trace of gas at all didnt even smell of gas at all. The compression also seems to be pretty damn low. I was wondering what caused this?... I think i know, i changed the clip on the needle a position and maybe its getting to much oil and not enough gas (would explain the no gas) and maybe all the oil caused the rings to some how get sucked into the piston a little (would explain the lack of compression) but iam stumped as to why its backfiring?? It has strong spark so i dont really think its electrical. Well thats my story, any help would be greatly apprciated and btw its a 1992 KDX200. The piston has about 50hrs or more on it (and i just put it in over the winter =). One more question how long do pistons last in KDXs?
 

Sage

dirtbike riding roadracer
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#2
sounds like you stuck it to me, check the compression and repost. sand loads the engine very hard and you said that you were only riding for 20 min's, if you didn't warm it up good you may have cold seized it. (thats when the piston expands faster than the cylinder) the backfire also sounds like the compression is so low that it won't ignite in the cylinder and loads the exhaust up with fuel then pops. also you said the plug was dry and the compression is low - seized.
 
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#3
Well..at least i no what caused it, now what ?

After removing the engine from the bike and taking the head and the jug off i found my problem. One of the circlips that holds the wrist pin in somehow come out of the groove and boom wore a nice long groove into the piston and an equally deep one right into the cylinder wall :scream: . Here
is a picture of the lovly piston, keep in mind there is an equally deep groove going just about all the way down the cylinder wall. My question is now what do i do??? Is it possible to even bore KDX cylinders? Its says they are electrofusion and cant be honed or bored in the manual, or am i going to have to buy a new sleeve??? Does anyone know who sell new sleves for a 92 KDX200 and how much they cost??
 

MADisher

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#4
talk to the man Fredette. I know he has prices listed on his web site for repating and and extra $40 or so if damaged. I don't know how dammaged that would include.

Your other options are:
a) a Steel sleve insert
b) pick-up a used jug (probably a Fredette option as well).

Since you mentioned you just did a Top end, it would be interesting to know if you used the Wiesco piston kit. Sage posted a warning that the pin was too long in some kits and that the cir-clips wouldn't therefore lock in. If you have/had one of these kits. I'd be bitchin to them for at least a replacement kit if not some spiff towards your head repair.

-MD
 
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#6
yup....

Yup, it was a wiseco piston kit. You think i could get some reimburstment out of them? Would it be worth all the hassel?....
 

MADisher

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#7
I would try... If you can still prove the pin is too long and not in spec. They should take care of you.

That is if they are customer focused. Now if you pooched it putting it toghether then.... :(

-MD
 
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#8
I read somewhere that Wiesco has had a recent problem with wrist pins being too long, so this could be the cause of the problem.

When you repair the cylinder, get it welded and replated. Don't get a sleeve if you can avoid it.
 

MADisher

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#10
My bad Sage...

Wasn't thinking clearly. Was just looking at Fred**** site so that's what I was thinking. Yes, they should prolly call you as well for pricing on such things.

But for the record, I've called the man twice and he's answered both times :confused: Though I know others complain that he's never there.

-MD
 

70 marlin

Mi. Trail Riders
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#11
sounds like big bore time !

just got off the phone with jeff! what guy :>¤¤ mr© gorr has a great deal on 2mm over bores© be for warned it takes time©
 

smb_racing

Master of None
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#12
I see no problem with boring the cylinder and replating (if necessary) but there's nothing wrong with putting a sleeve in. Just make sure you have a competant mechanic do the work. There's a guy not far from me that installs sleeves for $60. He guarentees the work to be done correctly or he refunds your money and pays to fix the defect. So far he's only had one return in 10 or so years of service.
 
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#13
The main problem with sleeves is rapid wear when compared to a plated cylinder. There is almost no damage bad enough that a cylinder can't be rewelded and replated.
 

MADisher

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#14
Sage, Fred, C-Dave what's your opinion on cylinder sleves ?

My 200 has almost 1100 miles on the top end with a sleve and I still have plenty of compression (190psi).

Perhaps I don't ride it hard enough ? I know spanky had a bad experience with a sleve, but let's see.

My 23 horse twin Kawi in my lawnmower has sleves in the cylinder, as does both of my tractors, not sure about my cars, but I believe the Excursion's v8 has em.

They are also a cheaper alternative to welding and plating. Now, personally since I bought the bike already sleved I'm stuck with it unless I want a new cylinder which I might consider at the next top end if enough folks can convince me that it's the better thing to do. Right now I'm not convinced.

MD
 

Sage

dirtbike riding roadracer
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#15
if the cylinder is already sleeved then worry about it on you next bike.