A bunch of Questions; HELP

[Guest]

Due to the symptoms of my bike, I should do a carb overhaul. BUT, if I can diagnose the problems before doing this, that would be wonderful. In a nutshell, the issue with my bike is.. All of a sudden:

The bike will not turn over right away, It it does catch, I have to really rev it to warm up. If I miss the window to rev it, it will not catch after that. If I set it to Prime, and leave it for a minute, gas will drip from the tube below. Sometimes it starts right up, sometimes not. Even after riding for an hour, I could very well stop the bike and then it will not start up again.

After many posts about this, people have given many suggestions on what it could be. I know close to nothing about what to do mechanically. Here are some suggestions from this forum as what it could be:

1. Petcock - Okay, easy enough, I replaced the petcock. Issue still remains

2. Gas Cap Vent- What is this? it was mention that there might be a leak preventing vacuum. Unfortunately, recently someone knocked my bike over, and I noticed that gas had leaked out of one side of the cap. Could this be the issue? It looks like the cap is on snug but who knows. I can definitley push down on the cap whens it's locked. Meaning there is definitely a bit of up and down movement. Maybe this is natural (Any more info on this how to fix, what tools I need to diagnose would be great)

3. Valves - Perhaps by valves are too tight. Bass Cliff has been kind enough to post a tutorial on this and aid me as to where to buy tools and gaskets.

4. Carbs - I've been told my float needles might not be seating properly. I will need to tackle a carb rebuild over the winter. Just don't have the time or space right now.

Is there anything I could be missing that could be my issue. What order should I diagnose and what tools do I need for each step.

thanks in advance for any help. I'm watching the end of the season pass me by and it's upsetting.

[jbs80106]

Fellow 650G rider here...

Interesting issue. These can be a bear to start sometimes but sounds like you're having more problems than most. Not a mechanical guru either but my logic and understanding indicates:

- To start the bike you need:
A) starter to turn the motor which moves cylinders up/down
B) fuel to get from gas tank to the cylinders via the carbs
C) spark/compression at the cylinder

- from your write up, sounds like its not A (assuming that its turning the motor fast enough).

- I'd suspect B (only because its the next logical part and may cause intermittent problems).

-- You replaced your petcock. Did you test with the rubber hose disconnected from the motor? Put petcock into 'normal' location and see if you get any gas out of the tube. You should not as its a vacumm system. There should be some way to apply some vacumm to the tub and see if fuel comes out. Don't ask me how, Only thing I can come up with is to suck on it...then switch petcock to 'Prime' and some gas should flow even without a vacumm.

-- Once you ascertain that fuel can get from the gas tank to the motor. Next spot to think of would be the carbs. I've not done anything with mine either. However, I would think that if a float wasn't seated properly you'd be having flooding problems or getting gas in the oil.

-- Probably need to check that you're getting spark at the cylinders required to ignite the fuel/air. I recall reading on here how to do that but I've not done it myself.

-- I can't help but think that the fact that you need to hold the throttle revs up to warm up isn't a 'clue'.

?? are you opening up your choke wide open when you're trying to start it?
?? do all 4 pipes heat up once you do get it started?
?? did you try keeping your battery charger connected incase the issue is the battery draining when cranking and not enough spark at cylinder?

Let me go back an re-read your post to see if anything else comes to mind. The statement that you sometimes have this problem when the bike is warm (i.e. get it started, ride, park turn it off and have troubles getting it restarted) probably eliminates some other potential items. My gut feels like its a fuel flow problem. I'd suspect that if it was something in the carbs it would be unlikely to effect all 4 cylinders..

Things that make you go hmmm.......

[t3rmin]

Let's keep it simple: your float valves *are* leaking, no "might be" about it. You're managing to get it started sometimes before it floods out, then riding it enough to use up the fuel faster than it leaks past the float valves, but when you stop it loads up again.

Don't spend another minute troubleshooting until you fix that. Give 'em a good cleaning and an o-ring kit from cycleorings.com.

[Dave8338]

Petcock: Not the problem (as it is new)

Gas Cap: Not the problem. If the vent were clogged, the bike would start and run fine and then, all of the sudden, just loose power and die. At that point, if you opened the cap, you would hear a suction sound as air rushed back in. It is normal to be able to "push down" the cap once it is seated and locked.

Valves: Not likely the problem as it would be consistant not intermittent.

Carbs: Most likely the culprit. As T3rmin has stated and I did as well in your last post, you float needles are not sealing. It also sounds like the choke circuits are plugged and in need of a good cleaning. When you have the carbs off, it is best to seperate the rack and disassemble each carb completely, soak them overnight in carb cleaner/dip and reassemble, using all new o-rings from RobertBarr aka. http://cycleorings.com/ . Once everything is back together on the rack, they need to be bench synched using a small diameter wire (I use a welding tip cleaner), making sure that all the throttle plates are set exactly to the same spacing, no exceptions. This will get the bike up and running and alow you to fine tune things from there. Check all parts (needle slide diaphragms are known to tear or get pin holes in them over time).

There is no short cut to fixing carb problems as they are the most critical portion of the equation and have the greatest effect on overall performance / driveability. You could try running some carb cleaner or Seafoam through it, though it is unlikely to do much for the choke circuit. :?