04 RMZ 250 long term problems/fixes

[shortyr6]

I purchased a 04 RMZ 250 for my for christmas. the bike is in good shape, but needed a little TLC. It looks great now, but we still have problems starting it. the kick starter moves with little pressure and turns the motor. I was told this was normal for this year group.

i did adjust the valves and we thought it helped, but back to the track we have the same issue. it wont run without push starting it.

SO....i have read a dozen or so threads on here about kind of the same problems. what is the long term fix for this year group bike?

If i send the head to someone like Eric Gorr, will that solve any valve train issues? i heard mention of a 2008 head will fit and solve the problems. I am up for suggestions of what has been successful and what has not.

I plan on getting in there and inspecting several things this week.

- hot start cable and assembly.

- adjust valves again if needed

- pull and clean the carb

- check compression

- try and buy a motion pro leak down tester to see if/where it may be losing pressure.

[Tha Breeze]

Sounds to me like you will need to refresh the head. They wouldn't sell the bikes like this, so if you rebuild the motor (or only need parts) then it should fix the problem. I would not ride a bike I had to push start.

I'm thinking either:

Ring > Piston > Cylinder

Valves and Valve seats > Head.

If you have the tool that rotates the cams and pushes the valves out great. I would suggest inspecting each one along with the seats, only a couple may be bad. But if you don't I would suggest taking the valves out and inspecting them and the seats. ***Make sure to keep all the parts together that goes with each valve, don't mix them up between valves. And know what valve goes where.

But hopefully it will be something cheaper such as a ring and piston. Are you burning oil by chance?

Also if you rebuild it make sure you inspect your oil pump, camshafts, buckets, and cam chain as well!

Edited April 4, 2012 by Tha Breeze

[shortyr6]

Sounds to me like you will need to refresh the head. They wouldn't sell the bikes like this, so if you rebuild the motor (or only need parts) then it should fix the problem. I would not ride a bike I had to push start.

I'm thinking either:

Ring > Piston > Cylinder

Valves and Valve seats > Head.

If you have the tool that rotates the cams and pushes the valves out great. I would suggest inspecting each one along with the seats, only a couple may be bad. But if you don't I would suggest taking the valves out and inspecting them and the seats. ***Make sure to keep all the parts together that goes with each valve, don't mix them up between valves. And know what valve goes where.

But hopefully it will be something cheaper such as a ring and piston. Are you burning oil by chance?

Also if you rebuild it make sure you inspect your oil pump, camshafts, buckets, and cam chain as well!

if i need to redo the head, i will replace the top end as well. it only makes sense to do it while i am that far into it.

i will pick up a leak down tester from pit posse tomorrow, so i should know a little more by the weekend.

when you buy used equipment, you get used problems.

[kawazuki250]

i bought an 04 with the same problems. I had to shim the valves, replace a head gasket, and re jet the bike entirely. Because it's a 04 kx250f twin, you can get away with using team green tech articles for that year to help with jetting (HUGE reason mine hated starting in general). I have a stock motor, and just making sure everything is in spec will make it fire up first kick, every time, mine has ever since i rebuilt the head. You can search for the 04 kx250f repair manual online and there's a free download for a pdf floating around, great reference troubleshooting guide in it as well. once you get everything right, that year bike runs great.

[Yacup]

best mod you can do is get, 08 kx250f rads weld new lower tabs on, re plumb coolant lines as per 08 setup. this will eliminate any overheating unless you sit idle for a long time. I am running a 270 kit in mine and used to overheat if i looked at my bike the wrong way!. since those 08 kawi rads went on, keeping the bike cool has made a HUGE difference on valve shiming and such. used to have to reshim more often but now since rads went in havent had to adjust in the last 40ish hours and still going strong.

[shortyr6]

welp, i have a feeling that i am getting ready to spend a lot of money.

I pressure tested the motor and i was getting a leak through the air filter. that told me i had a intake valve stuck open. so i checked the valves and shimmed the intake valve that was out of spec. nothing worked. i went to my smallest shim (120) i think and still it would would not get any clearance. so i pulled the head and it looks like the valve seat is collapsed a bit. the valve looks like its pushed in more than the other three.

the cylinder looks good, however it looks like there is a little wave around it about 4 mil in. i assume this is the top of the stroke for the piston. so it looks like i have to get this cylinder worked on or just get another kit all together.

it looks like i am about to put as much into the bike as i just paid for it. once again, used bikes = other peoples used problems.

so i guess i am on the hunt for a 08 head as some have suggested and a cylinder. or going to shop around to find someone to repair this cylinder.

cylinder works has a cylinder kit for $550

http://www.cylinder-works.com/ProductInfo.aspx?item_id=3764

Edited April 12, 2012 by shortyr6

[mog]

Its easy to spend as much on a old 4 stroke as they are worth, when buying you have to go through them with a fine tooth comb to ensure they don't turn into a money pit

[kawazuki250]

and chance you can send the head out for repair on the seats? I imagine it'd be cheaper than buying a whole new head

[shortyr6]

I want a long term fix. my understanding is that the 04-06 valve seats are the real problem in the head. in order to fix that, it seems an aftermarket seat or newer OEM seat will have to be used.

i am getting some pricing on having the head work done.

i also have a lead on a used 09 cyldiner and head that i hope will bolt right up.

[kawazuki250]

That's what i'm saying, send the head out to a engine shop of choice, like pro circuit does copper seat installs. I'd pass on the 09 head, not only is there a chance of it not matching the cylinder, but i'd be concerned about engine mount hole location, exhaust pipe location, spark wire sized properly, carb mounting to work with the airbox, etc. I know the 09 engine uses a FCR 39 carb and the 04 uses a FCR 37, so that may be an issue as well. The frame geometry of the 09 is also different than the 04. If you want to, go for it, but i'd rather send the head out for repair/upgrades than adapting a head that was never intended for use on an 04.

Edited April 14, 2012 by kawazuki250

[shortyr6]

That's what i'm saying, send the head out to a engine shop of choice, like pro circuit does copper seat installs. I'd pass on the 09 head, not only is there a chance of it not matching the cylinder, but i'd be concerned about engine mount hole location, exhaust pipe location, spark wire sized properly, carb mounting to work with the airbox, etc. I know the 09 engine uses a FCR 39 carb and the 04 uses a FCR 37, so that may be an issue as well. The frame geometry of the 09 is also different than the 04. If you want to, go for it, but i'd rather send the head out for repair/upgrades than adapting a head that was never intended for use on an 04.

after talking to a couple engine builders, they said to just buy a new head as it will be cheaper than trying to repair the head. just having new seats installed will be as much as a OEM head.

[Joshx221]

I believe the 09 head will not work. On a side note you are talking about kx heads right? I think up to 08 kx head will work, they did change the intake valvetrain a bit in 07 and you will need the spring retainers, spring seats, and possibly the tappets. The intake left on these year bikes are always the first valve to go. The problem isn't the seats its the head itself, around that valve is a hot spot in the head. The best thing to do is get stainless valves for atleast the intake side and better yet the exhaust too. Your head may still be good, but you have to take into account the condition of the cam journals. I just got my 05 head back from MX Time. Fresh cut seats and all new s.s valvetrain. 440 with shipping plus they cut the oil groove in the intake cam journal for me. They will tell you if your seats will not work before they do anything. So worst case your out 30 bucks shipping it there and back.

[shortyr6]

i got ahold of millennium tech. I am sending the head and cylinder out to them this week. hopefully in a couple weeks i will have it up and and running again like new.

[shortyr6]

got everything back from millennium technologies yesterday. everything looked great. new valve seat, valve guide, new valves, cylinder replated, and everything cleaned up.