04 Yamaha WR 250 - Kickstart Jammed

mj04uk · Two Stroke Sniffer Joined: 16 Sep 2009 Karma :

Well it seems every time I fix a fault, there is another one around the corner on this sodding bike !!

Latest, and I think fairly serious happened yesterday coming off a lane down by Clanfield Hampshire. Just pulled on the road and started to accelerate, into second and a screech from the engine.

Killed the engine and took it out of gear before pushed it to a safer spot the tried the e-start, which just clicked away (duff battery anyway). Tried the kick-start but this was jammed.

Took the cover off the started motor / idle gear and this all seemed fine and rotated one way as it should.

Removed the timing inspection cover and managed to get a socket on it and could rotate the piton without a problem, in doing so the kick-start would decompress, but without manually moving the piston the kick-start is jammed.

At this point I called for the recovery guy and waited a few hours looking with contempt at the bike Evil or Very Mad

Saw Blue and a few others on KTM's whilst waiting....

So any thoughts on what the problem could be or where should I start to rule out the easy fixes ??

I've pretty much lost confidence in the bike and the thought of dropping the engine and splitting the case to see what is going on is depressing to say the least.

First thought is the auto decompression on camshaft ?

mj04uk · Two Stroke Sniffer Joined: 16 Sep 2009 Karma :

Worse than originally though Evil or Very Mad

- snapped a valve and damaged the head and piston.

Thoughts ?? can it be repaired and if so suggestions of who can do it please ?

I have a spare piston, so can change that out but do not have the tools to remove the valves and concerned over the damage to the valve seat.

The bike is going to be sold, so do I take the time, effort and money to repair and sell it or cut my losses and sell as is or break it for parts ?

Blue_SV650S · World Chat Champion Joined: 27 Nov 2008 Karma :

Just seen this. Confused

You need to get the head to a cylinder head place to give an assessment on that valve seat.

Have you prised the valve head out yet and inspected the seat yourself? (pics plz)

The WRs have titanum valves, titanium is very light, but not overly strong, so you may get away with the head.

I have read that people who replace valves on WRs tend to go for steel replacements as they are stronger and therefore less prone to ... well snapping off Confused

... you might want to consider this.

The piston doesn't look like it has taken too much of a clout, so hopefully the bottom end will be ok?

p.s. Have you got a spare headlight?!!? Very Happy

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craigT19 · Jolly Green Giant Joined: 09 Feb 2002 Karma :

Titanium valves yes... weak, not really, half our range use these valves now without much problem. And from memory there not strictly titanium on the wr250. Yes they are titanium but the head of the valve is actually coated in a layer of metal similar to that of the barrel lining itself simply because on its own titanium cant cope with the extreme heat produced at the point of combustion.

Ive seen this happen on 2 other wr250s in my workshop and im afraid to say its going to be a new head, looking at the pictures the damage to the valve seat is (in my opinion) to bad to be repaired.

When did you last get the clearance's checked? off the top of my head the wr250f? needs a valve check every 11 hours? (say off the top of my head because i got the day off and have no service data to hand). Valve snapping in alot of cases (where the timing is correct) happens if the valve isnt seating right and the head from combustion heats up the valve stem and makes the valve snap where the stem is bonded on to the head.

When i get back to work next week ill make a few calls and send your pictures around if u dont mind? and ill let you know what they say.
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Bikes owned :- 2001 nsr125, 1999 zx6r, 2006 yzf-r1, 2009 xmax 250, 2012 yzf-r1, 2015 MT-07
Current bike : - 2016 MT-10
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mj04uk · Two Stroke Sniffer Joined: 16 Sep 2009 Karma :

Cheers for the advice, it was indeed a new head, fortunately I kept the old piston when I rebuilt the top end over the winter.

Valves clearances were checked the week before, however that particular one was a bit of a pain to get to so was going to buy a new set of slimmer feeler gauges to see what the clearance was - too late now !!

Anyway, the bike was all up and running a couple of weeks later, sailed through the MOT.

Blue - sorry no spare headlight.

chris-red · Have you considered a TDM? Joined: 21 Sep 2005 Karma :

mj04uk · Two Stroke Sniffer Joined: 16 Sep 2009 Karma :

Cheers for the advice, it was indeed a new head, fortunately I kept the old piston when I rebuilt the top end over the winter.

Valves clearances were checked the week before, however that particular one was a bit of a pain to get to so was going to buy a new set of slimmer feeler gauges to see what the clearance was - too late now !!

Anyway, the bike was all up and running a couple of weeks later, sailed through the MOT.

Blue - sorry no spare headlight.