640 hiccups

[gunnerbuck]

This is my first post of probably many : I am wondering if any of you 640 owners have experienced the following problem. I have an 03 adventure and every once in a while, usually out on the highway, the engine cuts out for a split second. This usually happens at around 5000 r.p.m and more frequently when conditions are wet. I first suspected water in the fuel and maybe the engine digested a droplet so I drained the carb a few times to put an end to that theory. It did it again the other day and it almost seems like an ignition cutout for a fraction of a second. Oh yeah once again it was wet [when hasn't it been in the last month in this part of the world]. The spark plug is fresh so the next thing I'll check is for any rubbed wires which could be shorting out. I'll have a good chance to do this when I have to repair the warranty repair on the leaky valve cover. [This seems to be a chronic problem with some 640s]. Anyways this hiccup is hard to diagnose because of its infrequent nature. Any ideas?

[LoFlow]

This happened to mine one time only. Under acceleration it just shut down and I pulled off to the side of the road. Hit the starter and away I went, no problems since.
These are very difficult to diagnose for sure. You may try to, at idle grab and lightly tug on all the wiring harness, relays, and modules you can see. Sometimes poor electrical connections or components will surface. At least when the problem gets worse it gets easier to find. good luck

[2 SPOT]

yeah sure sounds like electrical issue, difficult to diagnose. pay special attention to the wires comming out of the case for the,, stator? i had a problem once on my old KLR where the front sprocket/chain made contact once in a while with those wires.

[laramie LC4]

have you removed your smog cannister yet?

if not, it could be the problem. what happens is that you end up pinching the plastic tubing that runs under the seat going back to the cannister. when this happens it creates a vapor lock of sorts and cuts off the fuel. i had this problem with my bike when i first got it, it would just randomly die. once i removed all the emissions crap it went away.

do a search, there are several posts here and at ktmtalk about this mod....

good luck,

laramie

[meat popsicle]

Good suggestions already above. I would just add that if a shop is doing your valve cover "gasket" under warranty - read over creeper's how-to thread before you go. You might be convinced to buy a tube of that new and improved liquid gasket spooge that he recommends and give it to the shop doing your bike. That way you get the job done for free (hope they do it right) and the good spooge in there.

[creeper]

Hi Gunnerbuck,

Welcome to the asylum.

Aside from the areas to look at that are already mentioned, check the vacuum hose from the right side of the intake manifold to the fuel pump. In the past, this piece has kinked due to length and routing and the subsequent loss of vacuum renders the bike temporarily out of gas.

Also, when you remove the fuel tank to check and reroute the tank vent hose, check the spark plug cap to make sure it’s screwed on tightly to the high tension lead. It’s common for the lead to be a bit chewed up and sniping off 3/8” and screwing the cap on tight can restore a poor connection to its original sparkly self.

Thats all folks,
C

[gunnerbuck]

Thanks for the advice, this gives me a few more things to check in trying to fix the problem. Already had the warranty repair done about 8 months ago on the leaky valve cover, now its up to me to fix it right. I dont know the sealing product they used at the dealer, but I've got a tube of Yamabond 4 that I was going to try .Before I do, I'll check out creepers thread to see what he used.

[hawkster]

Gunnerbuck, I had exactly the same problem and took awhile to find. Under the seat near the battery I had a connector with 4 wires, two orange. One orange wire was disconnected/intermittent and possibly from time to time hitting the negative battery terminal. I soldered the orange wires together and problem solved. I got pi$$ed when it died on me 4 times on the way home at 50 mph in traffic. Most time it would start right up, or just lose power and regain again in a few seconds. Wires soldered under tape in pic.

[IMG]file:///A:/MVC-172F.JPG[/IMG]

[meat popsicle]

need an internet host for those pics hawkster. then [img]webaddress[/img] will make them show up.

for $40 a year smugmug will host all the pics you want; pretty damn good deal and a nice site (disclosure: the guy who pays for this site owns it so you'd be givin him some biz; nice payback eh?).

[neepuk]

Originally Posted by meat popsicle

need an internet host for those pics hawkster. then [img]webaddress[/img] will make them show up.

for $40 a year smugmug will host all the pics you want; pretty damn good deal and a nice site (disclosure: the guy who pays for this site owns it so you'd be givin him some biz; nice payback eh?).

Photobucket.com is free and soooo easy even I can do it.but if you got a few bucks, smugmug is way better!

[gunnerbuck]

Thanks Hawkster, that could narrow down my search considerably. I'll go check those connections right away.

[gunnerbuck]

The only wires I see near the neg. battery post go to the rectifier and they check out o.k. I guess this was to easy . I wonder if Noah is building, man is it ever raining outside. On the weekend I'll do a little more wire tracing, hopefully I'll find the problem. Thanks again for the tips.

My LC4 did the same thing. Over a couple of weeks time, it happened more and more. My problem was the "pulser coil" under the right cover was giving up and eventually failed. It also could be the ignition key, the next time it dies on you, reach up and turn the key off and then right back on again.

Good luck

[potatoho]

Check the kill/run switch on the bar as well.

[gunnerbuck]

Originally Posted by laramie LC4

have you removed your smog cannister yet?

if not, it could be the problem. what happens is that you end up pinching the plastic tubing that runs under the seat going back to the cannister. when this happens it creates a vapor lock of sorts and cuts off the fuel. i had this problem with my bike when i first got it, it would just randomly die. once i removed all the emissions crap it went away.

do a search, there are several posts here and at ktmtalk about this mod....

good luck,

laramie

This looks like it could be the culpert as my vent line had been rerouted and pinched under the tank . I think this happened while the bike was in the shop for warranty service.{ Thats a story in itself for a different thread} Anyways the smog cans days are numbered.