Engine seized from off cam timing?

[xz225f]

I want to get a '05 kx250f from this guy who says it was his practice bike. He explained that the cams got off timing and now it will not kick over. Would messed up cam timing really seize an engine? would I need to change the valve shims after I got the timing correct?

[urrick15]

Depends what they mean exactly. Some people may say it won't kick over, but actually mean it turns over but does not start. Usually the cam gear spins on the camshaft slightly and the engine will run poorly, or will not start at all. If the gear spins far enough it could cause a valve to hit the piston and possibly lock up the engine. Too many unknowns to say for sure.

[highmarker]

If it doesn't turn over the valves are hitting the piston, best that it doesn't start.   If the guy can't figure that out and fix it you don't want the bike. practice bike, LOL.

Edited April 15, 2019 by highmarker

[Drummer Rob]

+2

If the piston met up with the valve(s) that isn't an inexpensive thing to fix.

[William1]

Unless the bike was being sold for a few hundred, I'd walk, quickly.

While it may not be severely damaged, if it was insignificant and owned by a real racer, he'd fix it. A bike like that, I'd plan on a new crank, head, all valves pistons, barrel and cams. Not cheap. Shimming is the least of your worries.

[xz225f]

I am trading for my 96 xr100 and a  pocket bike so I am not worried about losing money. When I met him I will just open the cam cover, look at the valves and cam and put a little tension on the kick starter. Hopefully it looks good. And what do you mean a “bike like that”? And in what case would you have to basically build an engine just because the cams are messed up?

[William1]

4 hours ago, xz225f said:

I am trading for my 96 xr100 and a  pocket bike so I am not worried about losing money. When I met him I will just open the cam cover, look at the valves and cam and put a little tension on the kick starter. Hopefully it looks good. And what do you mean a “bike like that”? And in what case would you have to basically build an engine just because the cams are messed up?

Same reason you walk from a bike that 'just needs a spark plug to run'. A real racer with a practice bike, could fix the engine 'that just needs cam work' in a few hours and get a thousand more. How much is your time worth? The only way I'd consider a 'bike like that' is if I pulled the head and barrel and did an inspection first. It is a 14 YO bike with a potentially (and probably) trashed engine.

[notoriousE-R-I-C]

Sounds like a free bike(money pit) or keep shopping.

[xz225f]

When we meet I am going to inspect the bike. Remove side engine covers and cam/valve cover. Here is the link to his post: https://m.facebook.com/marketplace/item/380480919390964/?ref=messenger_banner

[76xtdrvr]

He has no clue what's wrong with it. If it won't kick over, it could be broken/bent valve(s), or cam(s) seized in the head, or a seized piston, or seized bottom end, or broken cam chain jammed onto the crank gear, or any combination of the above. Even if it does kick over but doesn't start, there could be a bad bottom end, cylinder and piston scoring, cam journal scoring, and bad valve seats. A 14 y.o. bike is probably not even worth parting out. Old, not running, and abused racing 4 strokes are money pits. 

[xz225f]

The guy said told me the he took it apart to find the problem and said that the cam chain tensioner had failed which of course would lead to jacked timing. He also says  that there are no signs of bottom end failure. There are plenty of pre 2006 bikes that are not beat to heck, y’all talk like they are ancient bikes that have been just abused and destroyed by their owners. I got my xr for $30 and it had been sitting for years. It is a ‘96 and in the 2 years I have had it I have ridden it past it’s limit and all I have done is change the oil.

[notoriousE-R-I-C]

If you're doing oil changes every 2 years...

[xz225f]

Its not racing the bike, it is a trail bike, and an xr. Y’all mxers are all about keeping your bikes prime and I could care less with a 96 xr100

[76xtdrvr]

1 hour ago, xz225f said:

I got my xr for $30 and it had been sitting for years. It is a ‘96 and in the 2 years I have had it I have ridden it past it’s limit and all I have done is change the oil.

An xr (great bike) and a 250f mx'r (also a great bike) are worlds apart as far as sophistication, internal stresses, cost to repair, and maintenance requirements. You seem to want to convince the naysayers here that it will be a good deal. All the best if you go for it. 

[xz225f]

Well I got some one interested to buy the xr with cash. Should I take the deal and buy a yz125 or trade for the 250f?

[notoriousE-R-I-C]

Yz

[xz225f]

the guy would not give me what I wanted for the xr, so I will get the kxf then trade for a yz or sell it for like 1700

[76xtdrvr]

5 hours ago, xz225f said:

the guy would not give me what I wanted for the xr, so I will get the kxf then trade for a yz or sell it for like 1700

Please post the condition of the kxf's engine when you determine it.  Hopefully, it's a simple fix. I would rather be dead wrong about a do-not-buy recommendation, than be able to say "I told you so".

[xz225f]

Thing was better than the picture. Looked like he cared for it really well, has pro circut coolant pump, kyb shocks, pro racing side cover. He said it died on him then he started it up for like 3 seconds then it died again. He then said he he took the valve cover off and saw that the cam chain tensioner had "failed". He said he did not have the tools or skills to fix it so he just wanted to sell it. I took the offer, and it looks good. It kicks over and has good conpression so when he told me it would not kick over i was worried but then i saw it and messed with it and the guy does not know much about it. Only problem is the tensioner he said was stripped. Should i try fixing it with a tap and bolt or blow 50$ on a new one? And where do i find one cause i have looked and have not seen them.

[notoriousE-R-I-C]

Use a time sert. And there are manual tensioners available.