Fuel related carby problem???

steve125

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#1
Oh boy did I just hava a scare!! :scream:  All is well for now but? I just started using U4 in my new kxf250. After some jetting the fuel works just great. My problem was this morning went out to work on the bike and noticed the hot start lever wouldn't pull in. Everything checks ok lever, cable, seems the fresh air piston was stuck inside the carb bore :scream: After alot of wd40 and some air pressure and finally a hard pull, it popped out of the carb. It was working fine the day before so what happened? There was a slight corrosion spot in the carb bore and on the brass piston. Cleaned it all up with some 600 paper and for now all is well. My first thought could it be the U4??? or was it just one of those mystery things?

Rich is it possible the U4 is responsible in any way? :think:  

Thanks Steve
 

marcusgunby

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#2
I think this new poster has the wrong forum-please banish him to the 4 stoke forum where he can talk of these issues:))
seriously ive heard people are experiencing problems with the KX/RM 250fs-maybe they have the same problem as you??
 

steve125

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#3
Oh! you just had to drop in with your 2 cents Marcus :confused:

I'm just courious if the fuel could be causing this corrosion. It may have come from the cable? This carb is shared by all the late model jap 4 strokes. So it's not a kxf or rmz problem. Ive heard of no problems with this bike so far. So we'll see ;)

 
 

bclapham

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#4
dont worry steve. i am sure marcus can hook you up with a couple of carbs from a 1978 RD350 that might work:confused:

i remeber you started a thread ages ago about the MXA fuel in thumpers and the o-rings on the carbs etc. Sounds to me like maybe a bit of machining debris or tight tolerance etc. but then again, i cant even figure 2 cycle engine out let alone a 4 cycle!:silly:
 
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#5
Most of these oxy juiced fuels have pretty high solvent properties so corrosion seems like a real possibility. The guys who run Nutec sure have run into those types of issues.
 

steve125

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#6
Bruce it wasn't a burr, it was corrosion. The bad part is it only took a tiny bit to lock that piston. Access to this piston is very limited when it's stuck, if it corrodes badly the carbs ruined! :( .......I think i'll cut the U4 50/50 with the mrxo1 that worked so well in the 139. Or unscrew the piston(cable) from the carb after every ride??......that sux :ugg: Just a note ive run alot of mr2 through my old 250f and crf 450 without this problem.
 
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#7
I haven't had any corrosion issues using Phillips B35 or P45 oxygenated fuels, or when adding my own oxygenate to basic leaded race fuels.

The fuels like Nutec (and possibly U4) that have a little something extra seem to be the ones that have these issues. VP has always been fairly tight lipped about exactly what is in their fuels so it's tough to say if what you saw was a freak event or not.
 

steve125

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#8
Rich, the wierd part is how fast this happened as it was just over night.

Thanks for your insight........Steve
 
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#9
Steve - Let us know if it happens again with the U4. If it is fuel related you should probably know in short order.

On to more important things, how do you like the KXF, and would you mind measuring and posting the OD of the exhaust system and the length along the pipe centerline from the cylinder head to the entrance to the silencer? Thanks.
 

steve125

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#10
The bike is real good except for the green :eek: But really i'm very impressed for a first year bike to be this dialed. The motor is excellent after break in. At first it's tight and a bit unwilling to rev, but that all changes by the end of the day. Next stand out is how it turns! A first for a kx on par with the cr. The suspension is plush, the shock more so than the fork. Ergo's are fine i did not find the bike cramped at all. According to our tape measure the cockpit is right there with the crf450. Jetting stock has been real good no hicups at all like the yz250f. The main is a bit rich and leaning that has helped top and over rev. I need more seat time but so far it's real good!

Rich i'll get that measurement soon! 
 
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#11
Cool, thanks Steve.
 

bclapham

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#12
steve: i am sorry i have nothing to help here, but do you drain your fuel after you ride? it sounds totally retarded, but why not run a carbs worht of fuel from the cr with oil in at the end of the day through the bike as a preventative measure until you suss out the problem?

Rich: i know there was some issues with the nutec stuff, was it corrosion or deposits? since i remember there active ingredient was isoprene which polymerizes easily and my hunch is that this is what causes the problems with that fuel- i know of a dude locally that was running it and he stopped since the stuff was too inconsistant, my hunch was the above.

so does this mean we will no have to go and buy spark proof laboratory refrigerators for the garage?????:silly:
 
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#13
Originally posted by bclapham
so does this mean we will no have to go and buy spark proof laboratory refrigerators for the garage?????:silly:
Bruce - It wouldn't be a bad idea. It's certainly simpler than the tub & buckets of ice water I have used in the past ;)
 

bclapham

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#14
hey steve:

it sounds daft, but i wonder if there is any methanol in the U4 as a cheap way to get the oxygenates up? the only reason i say this, is that i just changed a MeOH drum at work just now, we use these crappy metal hand pumps and it was covered in corrosion where it sits in the solvent (MeOH is mildly acidic and will also suck water from the air); to rest my mind, i looked at all of the other solvent drums and none were corroded, THF (an ether) and diethyl ether (very similar to MTBE) were fine as were the acetone and hexanes pumps.

the only other thing i can think was that the choke usually has a rubber boot on, maybe it wasnt seated properly from the factory and when you washed the bike maybe a tad of water got in there????

Rich: you are starting to scare me!:eek: :silly: did you get that paper on TEL i sent you? i am now having visions of you doing a TEL still in your kitchen; can just see it on the news, a downtown apartment exploded yesterday when a man was distilling petroleum products to sell to the local mx-punks LOL!
 
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#15
Originally posted by bclapham

Rich: you are starting to scare me!

did you get that paper on TEL i sent you? i am now having visions of you doing a TEL still in your kitchen; can just see it on the news, a downtown apartment exploded yesterday when a man was distilling petroleum products to sell to the local mx-punks LOL!
Yeah I got it Bruce. Thanks :yeehaw: I thought I had sent you a PM thanking you for it. Must be losing my marbles becuase my brain still hurts from trying to understand it all :eek: I'm looking forward to seeing Part II :thumb: It's times like this that I really regret cutting Chem classes in high school to test and tune on the little abandonded road drag strip behind the school ;)