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snglfin 01-13-2013 10:18 PM

'03 640adv troubles
 
hi all,

i have an '03 640adv with almost 30k mi on it. on my last ride, my hydraulic clutch lever began fading as my ride went on (of course it started when i was the furthest from home). at first it seemed to happen only at higher speeds (>50mph), and would feel normal after i slowed -- but then the fade returned, eventually at any speed. i got onto the freeway to get myself home with the fewest number of shifts possible, and after fifteen minutes my rear wheel locked up and the motor cut out. at 70mph. i pulled the clutch lever, but to no avail. i skidded over to the breakdown lane (it was an impressive distance, btw), checked my shorts, and got the bike into neutral and... it wouldn't start. turned over fine, but wouldn't catch. pushed it the last bit uphill and over to coast down to the next exit where i waited for my wife to pick me up.

i inspected the bike at home and took note of a few things:
-- fluid on the motor around where the clutch lever hose enters the gearbox (rh side, above sprocket);
-- fluid weeping around the shift lever/kick start shaft where it enters the gearbox;
-- when i cycle the kick starter a few times (slowly), i'm not sure i'm getting enough resistance (compression), though i believe i can feel when it's at the compression stroke. i'm not certain b/c i never use the kick start and haven't developed an accurate feel for it. i suppose i could compare cycling the kickstart with the decomp lever pulled vs not pulled (will try that tomorrow).

my initial thoughts are that gearbox trouble and engine trouble are two separate issues... but i'm new to this and wouldn't be surprised if i'm overlooking something. i would like to repair the bike myself, if possible, but am stumped at exactly where to begin the engine diagnosis. i know i need to check for spark and fuel delivery, but after that... what? is it possible i ruined my motor? when it turns over, i don't hear any new noises joining the usual racket that happens with an lc4, but as i mentioned, my experience is limited... does anyone out there have any insights they can offer regarding these bikes, with this mileage, and these symptoms (or any combination thereof)?

i sure hope i didn't kill my bike -- i'm kinda worried!

thanks in advance,
johnnyg

Tseta 01-14-2013 12:05 AM

First of all, thanks for providing a clear description of the problem, symptoms and such. Diagnosing at a distance is always difficult, so any and all relevant information is always very important.

In short, I agree with that the engine and clutch/gearbox issues are more likely than not separate issues. Some of the symptoms you descripe sound more than familiar to me.

1. The bike suddenly dying and refusing to restart, though cranking fine: one option is a failed intake side cam follower bearing. Read my experience here (the start of that particular saga), more general documentation and discussion here (all pages).

2. The clutch changing it's feel along the way may simply be either the master or slave cylinder (or the respective seals) coming to the end of their useful life, causing the leaks. A rebuild with new seals may be all that's needed here. Other option, which is actually totally separate from leaking seals but causes somewhat similar symptoms is well detailed in these two threads, here and here. I recommend reading all the pages of both threads closely.

3. The leaking shafts are a known issue with the LC4 (see here or here for the fix). However, if the start of these leaks coincides with only this "incident", I would be willing to wager there might be something more going on inside the engine. It is not unknown for the transmission bearings to let go, allowing the transmission shafts to wobble around excessively in the cases, causing all kinds of damage (one fairly mild example here).

All in all, I think you need to do some further diagnosing. However, I envision a engine-opening excersise (case-splitting) in your near future. For that, some good reads (besides the LC4 index thread with links to multitudes of info, you are familiar with it already, aren't you?) are these:

Gunnerbuck's 127,000km rebuild thread
ClintNZ's rebuild thread
Three times the fun! - rebuild of 3 LC4's
LC4 routine maintenance

...and many more of course, links can be found from the index thread. :deal

Cheers,

Tseta

snglfin 01-14-2013 07:40 AM

thanks for the input tseta... as a n00b, i'm trying to gather as much info as possible, and then sort through it as i think it applies to my bike's issues. i'm hopeful my clutch lever line is what's leaking down at the gearbox, causing the lever fade. the links you provided are really helpful -- the discussion regarding the graduated bearing retainer is ringing some bells for me. i'll do more investigative work next weekend and hopefully have more info to share.
i really appreciate your time and insights.
regards,
johnnyg


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