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

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Posted by: At0m1c FuSi0n---------------------

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?


Posted by: Sage---------------------

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.


Posted by: At0m1c FuSi0n---------------------

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??


Posted by: MADisher---------------------

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


Posted by: MoO_coW---------------------

Looks like a wiseco to me.


Posted by: At0m1c FuSi0n---------------------

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


Posted by: MADisher---------------------

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


Posted by: spanky250---------------------

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.


Posted by: Sage---------------------

Quote:
Originally posted by 88RM250
talk to the man Fredette.


Or you can call someone that will answer there phone? :think


Posted by: MADisher---------------------

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


Posted by: 70 marlin---------------------

just got off the phone with jeff! what guy :>¤¤ mrİ gorr has a great deal on 2mm over boresİ be for warned it takes timeİ


Posted by: smb_racing---------------------

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.


Posted by: spanky250---------------------

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.


Posted by: MADisher---------------------

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


Posted by: Sage---------------------

if the cylinder is already sleeved then worry about it on you next bike.


Posted by: spanky250---------------------

Quote:
Originally posted by 88RM250
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.
You are comparing apples to oranges. None of these engines turn anywhere near the rpm's that a bike engine turns, nor do any of them see the rough service that a dirtbike engine goes through. Cars are not driven around at large throttle openings all the time ( at least, not most of them ), and the lawnmower and tractors run at a constant, low rpm. Those engines also have cast iron pistons as well as the cylinders, so the expansion-differential is not a problem, either. Also, four-strokes with iron sleeves tend to get much better wear from the sleeve than a two-stroke, although I don't really know how to explain why this is.


Posted by: canyncarvr---------------------

BTW..
Quote:
?... I think i know, i changed the clip on the needle a position and maybe its getting to much oil and not enough gas


For future reference, troubleshooting, whatever....this is completely wrong. While you may cause a mixture problem (lean/rich AF..air/fuel mixture) by changing the needle position, you will NOT cause a ratio (premix) problem.

The one has nothing to do with the other.

Well, unless this is one of those bikes that has the oil injected through the needle jet???:silly:


Posted by: Canadian Dave---------------------

There are pros and cons to each. My personal preference would be to have it replated.

Given you need to repair it anyway you may as well make some improvements. I'd suggest looking into having the cylinder opened up to a 220 and ported. There isn't much difference in cost and you can tailor the power to your individual needs.

David


Posted by: At0m1c FuSi0n---------------------

The local shop (dont know if there very bright or what) claims that the cylinder cannot be bored and i have to buy a new one ($450) or have if resleeved which they said would cost around just as much as a new one. Do they not know what there talking about or is it just me?


Posted by: MADisher---------------------

Yep try another shop.

Well, not having seen the cylinder... I would assume it could be welded, cleaned up and plated. Fredette quotes " Cylinder replating. $180.00 If its damaged add $40.00 " on his web site. Sage ? chime in here with a quote.

More importantly your shop is figuring they can't make much money on this and probably just don't want to do it. I know there are two shops here in Cincy that won't even touch motors in the summer time (which is ludicrous IMHO).

good luck, let us know what you come up with.

-MD

P.S. You could buy my RM 250 and stick that motor in your KDX frame with some modifications


Posted by: 70 marlin---------------------

can you say over bore?


Posted by: smb_racing---------------------

his shop may be right, if the cylinder has been bored/plated many times before it could be that it has to be resleeved.


Posted by: MADisher---------------------

Quote:
his shop may be right, if the cylinder has been bored/plated many times before it could be that it has to be resleeved.


Agreed, for some reason I was under the impression that this wasn't the case. None the less it is summer and a lot of shops (at least around here) just don't want to tear into motors in the summer. However, sounds to me like he'd just be bringing in the cylinder. I'd still get a second opinion.

-MD


Posted by: spanky250---------------------

The dealer isn't exactly lieing to you, they just aren't telling you the entire truth. Your cylinder can't be bored in the traditional sense, like a steel sleeve can be bored and fitted to an oversized piston, but it can be rewelded to repair damage, and replated to the stock bore size, or you can go with a big-bore kit. A big bore kit consists of machining the cylinder casting to the dimensions of a larger piston, and replating the cylinder to the correct bore size for that larger piston.


Basically, there is not very much that can prevent a cylinder from being repaired by some method. One of the few reasons that can prevent you from repairing it is if the valve pockets are worn out or damaged, and even that can usually be repaired for a price. Even cracks can be welded, and the cylinder replated afterwards. smb does have a point, though, a cylinder can not be repaired an infinite number of times.

If a cylinder is truly too damaged to be replated, sleeving is still a viable option, although a poor one in my opinion, a route I would choose only if the only other option was to shell out $500 smackers for a new cylinder.


Posted by: At0m1c FuSi0n---------------------

How much would getting in sleeved cost?... I know some very experienced machinist that could just punch the current sleeve out and press the new one in. Then do i have to have the new sleeve bored or do they come the right size? I plan on selling it right when it gets fixed and buying a new KDX220 or a KTM 250ex/c so sleeving it wont bother me =).


Posted by: Canadian Dave---------------------

They will bore the cylinder, install the sleeve and bore the ID of the sleeve to match the piston. . . . . Yes they will have to bore the sleeve.

David


Posted by: spanky250---------------------

One important thing to consider before you pick a machinist to sleeve the cylinder is that installing the sleeve is only half the job. You also have to cut port windows into it and match them to the ducts, and they have to be chamfered properly.


Posted by: Sage---------------------

am I wrong here? I thought you said the cylinder had already been re-sleeved by the past owner? is it sleeved or not? if not re-plate the darn thing. sorry I can't quote a price or that would be spam, and I can't say to call or thats spam also. but if your surfing around and you click the website button down there you might find a phone number on the site. also I just did a 97 CR250 cylinder that was trashed, blown crank & a broken piston, big rips in the cylinder walls, it was the worst cylinder I'd seen and that was $225.00 total cost to fix, welding, boring, diamond hone & shipping. if the cylinder has been sleeved then there no turning back. see ya!


Posted by: MADisher---------------------

Sage, I dun see no website button.


Posted by: woodzracer---------------------

A few years ago my KDX was stolen and run through Baltimore city for three weeks on straight gas. Needless to say when I got it back it wasn't pretty. When we tore it down the cylinder and piston were garbage. I sent the cylinder out for replating (not sure which company but check the back of the magazines) When I got it back it looked as good as new and has run for about four yours without a hitch. If I was in that position again (or in your shoes, I would definetly replate and go with an oem piston. Good Luck



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