Jump to content
Sign in to follow this  

Guys, I need HELP K5 RM250

Recommended Posts

I have a K5 RM250 2 stroke that is giving me grey hair. It has been a real bear to start when cold and can take 20 minutes of kicking to finally get it to fire.

A Suzuki mechanic friend of mine looked at it and said if it doesn't pop in the first kick or two something is wrong. He thought maybe there was an electrical problem with the kill switch so we disconnected it and SHAZAM, it fired on the first kick... Problem solved!!! not so fast....

So, I replaced the kill switch and the problem resumed, so I replaced the entire wire harness, no luck....

Then I took the bike to the Suzuki dealer and told them about the problem... They said, "It was just a fouled spark plug, that'll be $200" problem not fixed, still a bear to start.

When the bike does finally start, it is a mosquito sprayer for about 2 minutes and visibility at the track is temporarily reduced to a 1/4 mile in smoke. Once the bike warms up, it runs fine but is a little rich (jetted one click richer than stock)

So, my next attack plan is to pull the carburetor and clean it out because maybe there is crud in there??? and also possibly replace the CDI (electrical brain).

Does anyone have any ideas???? THANKS for the replies...

Share this post


Link to post
Share on other sites

Have you checked your transmission oil lately? See if it is low. Could be a leaky crank seal?

Share this post


Link to post
Share on other sites
Have you checked your transmission oil lately? See if it is low. Could be a leaky crank seal?

👍🤣

Share this post


Link to post
Share on other sites

When was the last time you did a top end? A piston on a modern 2 stroke only has like a 20 hour life!

I blew a tiny hole in mine and it would run, but was impossible to start.

2 strokes are super simple. Its probably not electrical - electrics on these bikes are pretty rock solid - but you could pull the stator-side cover and check as often dirt gets in there and mucks things up.

Air/Fuel/Spark

start with the obvious stuff and work backwards.

Share this post


Link to post
Share on other sites
Have you checked your transmission oil lately? See if it is low. Could be a leaky crank seal?

This is entirely possible, but I would still check the carb first. Any bike that's been kicked 20 times will be close to being flooded out, so a cloud of smoke after it finally fires up would kind of be expected.

But again, its easier to pull the carb and dip it. And pay special attention to the choke and pilot circuits, after all these are the circuits that your bike uses when it first fires up. And make sure that all of your settings are correct (idle, air screw, needle and float height). And for what its worth check the spark, a nice fat and blue spark will tell you that the the electrics are fine ~ or not.

Share this post


Link to post
Share on other sites

Thanks for the replies!! I think tomorrow I will pull the stator cover and have a look and then pull the carb and start cleaning.

If that doesn't work then I'll pull the head.

This RM250 is being a PITA. I'm not a Honda fanboy or Suzuki hater but in 30 years of riding I have never had issues like this with my Honda bikes. Even my kids Yamaha TTR-125 is being a pain due to a design flaw. The way the choke cable was designed on the TTR allows water to leak down the choke cable and into the carb causing corrosion which deforms the barrel. I had to replace the carb and rejet....

Share this post


Link to post
Share on other sites

What do you consider low for compression?? The bike is a 2005 but I'm pretty sure it has never had a top end job. Don't these 2 strokes need that after about every 20 hours or so?? I'll check compression and report when I get back home. Thanks for the replies!!

Share this post


Link to post
Share on other sites

05 and never changed the piston!!! i think we all know what the problem is

Share this post


Link to post
Share on other sites
05 and never changed the piston!!! i think we all know what the problem is

I have had many bikes including my current GSXR-1000 K7 that I track. All of these bikes are four strokes so I have to admit that this is my first two stroke that I have had for long enough to do maintenance.

I work on forced induction systems (superchargers and turbo systems in cars) , custom fuel mapping and ignition, and suspensions but I have never ripped into a two stroke.

So I take it that the consensus is that the piston rings are probably worn out and there is likely low compression and that by installing a top end kit, I can rejuvenate the RM250 and it should start a lot better??

Does the piston get eaten up or wear out after so many hours of run time?? I am referring to the quote above and don't quite follow..Is it the piston getting trashed or the rings???

How hard is it to do the top end?? I do have the Suzuki shop manual and it doesn't look too bad at all but, any tips or gotchas to look out for??

Thanks everybody for the replies.

Share this post


Link to post
Share on other sites
05 and never changed the piston!!! i think we all know what the problem is

Woah woah, ive been runnin my RM hard and frequent for the last 8 years on the same top end with no problems, and it still runs strong, ive probably put 20 hours on in the last 6 weeks.

If you can turn it over with ur hand easily then yes probably gonna need some rings but if theres a decent amount of resistance on the compression stroke that should be enough to make it fire.

dont jump to the top end conclusion just yet

Share this post


Link to post
Share on other sites
Woah woah, ive been runnin my RM hard and frequent for the last 8 years on the same top end with no problems, and it still runs strong, ive probably put 20 hours on in the last 6 weeks.

If you can turn it over with ur hand easily then yes probably gonna need some rings but if theres a decent amount of resistance on the compression stroke that should be enough to make it fire.

dont jump to the top end conclusion just yet

Well maybe I'll start with a compression test before I order the TopEnd kit....

Back to the original post on this thread, I mentioned that by disconnecting the kill switch the bike fired right up. I replaced the kill switch, the kill switch wires and then the entire bike main wire assembly and the problem resumed. Could it be some kind of electrical issue with the CDI???

More grey hair popping out.

Thanks for the replies.

Share this post


Link to post
Share on other sites

Check your reeds. A new top end would give you the peace of mind, but I would check the reeds right now to see if they are chipped or broke. If it idol good then it wont be the reeds, but you didnt say if the bike idol good or I missed it.

Share this post


Link to post
Share on other sites
Check your reeds. A new top end would give you the peace of mind, but I would check the reeds right now to see if they are chipped or broke. If it idol good then it wont be the reeds, but you didnt say if the bike idol good or I missed it.

Once the bike gets started, it idles fine (little rich) and runs pretty strong but it is just crazy hard to start when cold.

I'll look at the reed valves too though. Thanks.

Share this post


Link to post
Share on other sites
I have had many bikes including my current GSXR-1000 K7 that I track. All of these bikes are four strokes so I have to admit that this is my first two stroke that I have had for long enough to do maintenance.

I work on forced induction systems (superchargers and turbo systems in cars) , custom fuel mapping and ignition, and suspensions but I have never ripped into a two stroke.

So I take it that the consensus is that the piston rings are probably worn out and there is likely low compression and that by installing a top end kit, I can rejuvenate the RM250 and it should start a lot better??

Does the piston get eaten up or wear out after so many hours of run time?? I am referring to the quote above and don't quite follow..Is it the piston getting trashed or the rings???

How hard is it to do the top end?? I do have the Suzuki shop manual and it doesn't look too bad at all but, any tips or gotchas to look out for??

Thanks everybody for the replies.

a topend is pritty easy to do on a 2t just take you time and be patient (i'm 13 and can do it)

what i dod not think about before is it could be a falty cdi or maybe even a stator

Share this post


Link to post
Share on other sites
Once the bike gets started, it idles fine (little rich) and runs pretty strong but it is just crazy hard to start when cold.

I'll look at the reed valves too though. Thanks.

Sure sounds like a worn topend to me. Typically an OEM topend will last about 25 hrs depending on the riding getting done. With Wisecos I get about 50-60hrs riding MX and I know alot of guys that get way more hrs than that riding trails. 150+hrs.

If you haven't done a topend yet I would do so before it costs you more than just a topend kit. $$$$$

Good luck

Share this post


Link to post
Share on other sites

Unless I missed another change to the 'kill switch', if it were me, I'd disconnect the damn thing (wire it together) and say the hell with it! Leave the wires exposed or set up another 'opposite' switch letting you rip the kill switch wires apart to kill it.

Share this post


Link to post
Share on other sites
Well maybe I'll start with a compression test before I order the TopEnd kit....

Back to the original post on this thread, I mentioned that by disconnecting the kill switch the bike fired right up. I replaced the kill switch, the kill switch wires and then the entire bike main wire assembly and the problem resumed. Could it be some kind of electrical issue with the CDI???

More grey hair popping out.

Thanks for the replies.

Hmmm... with electrical issues like that, I'd check the gap in the plug and see if I could reduce the gap by a little.

Share this post


Link to post
Share on other sites
Unless I missed another change to the 'kill switch', if it were me, I'd disconnect the damn thing (wire it together) and say the hell with it! Leave the wires exposed or set up another 'opposite' switch letting you rip the kill switch wires apart to kill it.

I am with this one. If I unhook the kill switch and it starts right up. I then hook it back up and now it back to not starting. I would unhook it and find the short. Top end doesn't have anything to do with the electrical side of this.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...