Posts
8
Joined
1/9/2020
Location
Wales, MA, USA
Hi all, hoping to get some advice. I have a 2024 KX 250X big end on the Connecting Rod went. I reassembled my crank with a ProX rod and set the width. I then trued the crank and when I was done the Crank width is now .003" smaller than the one I took out. I don't have a service manual and I need the bike this weekend. Hoping someone with more knowledge or experience could help me out. I don't want to try to shim it out as the more you mess with it the weaker it will get. I don't see it being a huge issue as everything pulls tight to the primary on assembly. It would throw my timing chain alignment off by .003". Anyone with any info or experience I would appreciate it. Never had this happen before. Thanks in advance.
To me, the Key / Most Important Measurement is the clearance at the big end.
Have you set that to the correct measurement / clearance?
As in, is it Not .003" too tight now?
If you've got the correct clearance at the big end - and That is Very, Very Important , and the primary side is tightening to a 'stop' against the primary set up, I'd think .003" at the other, LH side, may not be an issue. The bearing journal on the LH looks quite long, so it appears to have No danger of Not being fully into the LH bearing ( which is listed as being the same both sides ) , and the cam chain sprocket is up against said journal end. But, be wary with my opinion - I've no real experience with your bike, so, be careful.
Hopefully someone that knows the bike, can chime in.
My current assembly has a side clearance on the rod of .009". Which is actually what the stock one measured but it was burnt and probably not accurate. The babbitts were gone. I've reached out to local Kawi dealers to no avail. I need to order a service manual but they are hard copy and I won't have it in time.
Strange failure, 65 hours on a stock motor with great maintenance, everything else appears healthy.
I appreciate the feedback.
If a Kawasaki Dealer can't / won't help you with the measurements, I would try contacting an engine Specialist - eg Pro Circuit / others. You know, people that actually work on your engine type.
As .009" seems a bit tight to me - but as I wrote, I don't really know what a 24 KXF250 needs for clearance.
There's nothing worse than rebuilding an engine, and 'lunching' it promptly, due to too tight a clearance in such a key component - and Big Ends really really cop a hiding with high revving engines - well, every aspect of 250Fs cop it.
So a local Kawi service dept called me back and said the rod clearance was .25-.35mm so .0098" min. They don't have a spec for total width. He also stated they don't replace connecting rods just the whole assembly. He understandably wouldn't give me a recomendation. I am in a bit of a pinch, headed to Tennessee for the GNCC, I think I am going to risk it, being under by .0008" I don't have any .0005 feelers but I can get the .009 in easily but the .010 will not go in. 8/10ths of 1 thousandth we'll see what happens. I will update after the weekend.
Thanks Bearuno.
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I just did one last week on a 21 250x. Outer crank width I measured at 2.246 I believe.
Important part is the rod clearances as long as your in the proper rod clearances you should be good to go. Cranks will "loosen or set" a bit from use or even from the rod going out. So not uncommon to be slightly different in widths from the used to the new/rebuilt. You might find it back to the previous width when you pull it out next time.
Not your issue but, one thing I preach to people if you buy a crank and it's not welded in place make sure you roll it through and check everything. Most common reason why hot rods cranks go bad. People don't check the fit and run outs. That shit gets dropped, kicked and bounced around.
If rod clearances are good and your widths uniform which should make your runout good you should be fine. Lots of people do more damage during install than anything so make sure to be careful there.
Also try crank works, Carrillo, hot rods, hp performance, pr2 they will all have an answer for you.
Crank width was 2.253 when I pulled it, the one I just put in was 2.250. It was uniform and runout was within .001 on the far ends away from the bearing journals. Froze the crank overnight and heat gunned the cases for 10 minutes everything went together smooth. Bottom end is in the bike. Cleaning up the valves and putting new valve seals in and hopefully finishing up tonight after work. Fingers crossed.
How did it work out for you.
Okay, with one potentially related hiccup. About 6 miles in I was lazy on the clutch and stalled the bike in a gully of course. The bike would not turn over, no clicking, nothing. I flagged down a 4 wheeler (lucky) to see if he had tools to check my battery connections. This was after sitting for 4-5 minutes. He asked what's wrong and I hit the starter button to show him the "nothing" and it fired right up. I then rode the rest of the lap easy as not to stall and made it back to my pit where I had tools. I shut it off and it fired right back up. Ran fine for the rest of the day 2.5 hours total and I stalled it a few more times but it acted normal the rest of the day. Any ideas?
I should add I haven't checked anything yet, threw the bike in the trailer and then drove the 15 hours home. At work now and will go through it tonight after a cleaning.
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