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Could it be some leak from exhaust valves? Valve springs that stretch while warm? I know You have rebuild it lately, but… Maybe some human error? How long since rebuild? Did she ran OK after rebuild?

As for the starter - I renewed brushes in mine just 2 days ago. It starts way better but my starting behavior didn't changed at all. I don't think it will help but surely You can give it a go and check. I can't think of the any temperature related starter problem that would cause such behaviour.

Did You checked the air filter as well? Oiled it recently? How is the sparkplug looking? Coil? Any blown fuses recently? Something that would point us in the direction of the problem?

You usually make photos while assembling - how was the deco/autodeco looking?

A propos backfiring… is it a loud BANG after You just trying to kickstart? Once or more pop pop pop like when deccelerating and engine braking?
A loud bang would be probably the fuel fumes that leaked into the exhaust and got ignited. A series of pop pop pop would mean… well I don't know

Its along shot - you may have seen this post below. Gaspipe may have an angle on it.

http://www.advrider.com/forums/showpost.php?p=877603&postcount=692

Tseta;

Any way the choke is sticking?

Is your throttle slide/guide worn? If it is, the needle emulsion tube will probably be worn also.......causing a too rich mixture?

These are just guesses Tseta, good luck.

More info, answers to questions asked:

The exhaust (and intake) valves are new, as well as the valve springs, collets clips, spring retainers, etc. Basically, the whole valve train received a refreshesment during this rebuild.

It has been about 500km since the rebuild. It ran without much trouble for about 250km, and then started having these troubles. My riding has been quite on/off during this spring, so I can't really say if it truly has been a gradual or a sudden change.

Immediately after the rebuild, the bike seemed to run just fine, no problems to speak of. Even now, there only exists the problem of very difficult starting with the e-start, when warm.

I'll take a look at the starter, but it puzzles me, shouldn't it be even more difficult to start when the bike is cold.

Air filter should be OK, not dirty, but not oiled very recently either.

Spark plug looks normal, like this: http://www.gnttype.org/techarea/images/plugs/champ1.jpg

I haven't checked the coil yet, no fuses are or have been blown.

I didn't disassemble or take a closer look at the autodeco on the new cam, I (perhaps incorrectly?) assumed that it would be correctly assembled and functional from the factory.

The backfiring is usually a single, loud bang. It may happen when kicking the bike, just as the bike fires up. It may also happen at the end of cranking with the e-start, when it fails to start. Sometimes, it even pops when kicking it, and failing to start.

This seems to be a very difficult and frustrating problem. My information probably does not help much with the diagnosis either. However, I truly appreciate all the responses so far. I will have to do much more checking on the bike, tomorrow.

Cheers,

Tseta

Edit:

Choke is not sticking, this was verified when taking the carb apart. The throttle slide/guide are not worn either. Needle and emulsion tube are like new, also. As I said, stumped... Sigh.

Happens to me too when I kickstart her but only after I hold the manual deco to get just past the TDCC. Usually when I blow it up and fail to kick it rightly. I assume the fuel is there, the spark is produced and it fires up into the exhaust. First time she did that I almost pinked in my pants.

I assume You checked the manual deco while assembling, and right now for tension in the cable…

The autodeco hypothesis looks even more plausible…

Yes, I checked the manual deco as well. I keep the manual deco cable as slack as possible, to make sure that it is not "hanging up" by accident.

If it turns out to be the autodeco, I am going to be quite pissed off. A brand new cam causing troubles is definitely not OK in my book...

-T

T;
I'm going back to the coil.....enough voltage and cold coil to start when it is cold. Hard starting due to short when warm. Coils show symptoms when hot sometimes. Less resistance when cold.

Another thing to think about.........just because a part is new/rebuilt.....does not mean it will work correctly.

Keep us posted.........I am sure you will figure it out.

Cheers

As I have mentioned some time ago I have managed to fry my cables for the fan from the hot exhaust. It was related to the valve check I did before. It was extremelly hard to start and then impossible even as the coil did not have had enough juice to produce a spark.
Thinking of it… as You run - maybe some electrical equipment is draining the battery and causing the problems with starter when hot. Or maybe the ignition point got misaligned? And the starter sprague clutch? That can't be it.

I'm with the Dropatrotter with the coil. That could be it. Maybe a cable vibrates and rubs somewhere and shorts? When cold the starter cranks right away because it has no problems without vibrations & warm.

If not this could You elaborate on starting procedure of Yours? Choke or not? Throttle or not? Just curious - perhaps there is some peculiarity You didn't though about.

Tseta, is your float needle in good shape? I've had mine go bad in the past and it causes all kinds of starting headaches... The rich condition a worn F-needle causes will get worse when the engine is warm...

Also make sure to inspect the wire cluster going into the CDI for wear abrasions... Also pull the CDI plug out of the unit and flush with contact cleaner and then apply electric grease to make sure it is getting full contact...

I've had the ignition systems go bad on chainsaws and other small engines as to where they run cold and outright quit working when the engine gets warm ... My experience with motorcycles are that they just quit all together when the CDI goes bad... I have had spark plug caps fail as well causing erratic running...

Gunner, Alik, Overlandr and Droptarotter: Thanks for the advice so far.

I realize that it might be "bad form" - cluttering up this mega-thread. The issues with my bike continue. In addition, the blue 1998 has started showing some post-rebuild hiccups as well. Thus, I'll be moving this discussion to my own "Three times the fun"-thread.

It has been a very long day for me, trying to diagnose all these problems. The fact that they are perhaps electrical (or at least related) and at times, intermittent, makes it quite difficult.

Major headache...

I think I may have some cold liquid headache medicine in my fridge, though...

Cheers,

Tseta

Kippis to that! :)

Maybe in left field. maybe not.

Old '74 XLCH 1000 (points & condenser ignition)- backfiring, with flames shooting a couple feet out the pipes indicated that the points had "slipped," point gap had closd up, and points plate had rotated . increasing advance (I think - it's been a long time since I converted to electronic ignition). Is this possible with electronic ignition? Dunno, but if the Hall effect or whatever trigger is used has "slipped," I think so.

Hard starting with electric starter on a '82 FXWG or '78 FXE (don't remember wihch, same starter system anyway) when hot, OK when cold - corrosion in the + cable to the starter solenoid, not on the terminal but within the cable itself. Finally noticed the cable was swelled, took it off and, inside the insulation the copper was gray-green and powdery. Bent thje cable back and forth a couple of times and it broke into. When hot, resistance in the cable increased and she wasn't getting enough juice to spin the starter. This is possible on anything.

Probably no help but maybe a direction in which to look.

Hello everyone, I just purchased a 99' 640 Adventure and the Tripmaster is almost unreadable. I've read some of the archive posts on ideas and thought that I'd try silicate packets(moisture maybe), but other than that is there anything else that can be done to still measure mileage and speed? Can a GPS unit do this? Thanks for any ideas.

I'm no electrical expert, not even a novice Yes a GPS can do this but it may be more difficult to track hours/miles for maintenance intervals and impossible to quantitatively track total mileage for resale purposes. I've read of some people using the Vapor for a replacement or upgrade. If you go this route I'd take a picture of the mileage/hours on the tripmaster when adding the new unit so you will have the total mileage/hours for the motor if you do sell it down the road.
Hope this helps,
Gerst

http://trailtech.net/motorcycle_vapor_kits.html

BTW where on the western slope are you?

link to flea market post
http://www.advrider.com/forums/showthread.php?t=681171

Gerst- I'm out of Grand Junction. Thank you for the reply. I knew the GPS would do speed. I just don't have any experience with one. I will have to check out the Vapor units.

Mars- Thanks for your link, I'll check on it when I get back from work.

Hello all!!

Just did my first roundabout with her since its transformation from supermoto.... love it !!!!!!!!

my bike , with many mods . just added my mates 2001 adventure too

Many Mods I see!

How much did the twin disk set up run ya???

Also what kind of pipe are you running. That sure is a pretty blue! Matches the bike!

Nice bike indeed!

That's an Akrapovic titanium header by the way, only works together with the (in Europe non road legal) matching muffler.