Bogging down/Stalling Problem

[BrysonK]

Hey all,

My bikes been riding good lately, and then all of the sudden out of no where, after 10~ minutes of riding, it will begin to bogg down/miss in mid-range RPM, to the point where it will bog right down and stall out. It is then very difficult to start after. Now it is having a hard time to start when colder, and has bogged out/stalled a few times after a few minutes of riding.

Any suggestions on whats going on here?

Thanks
BK

[ivkat]

I think this problem is pretty common with our bikes, especially if they are older. The same thing happened to me, and i had the carbs cleaned and replaced the needles and floats in the carbs. You may just need to give them a good cleaning and adjust the float level. Hope this helps.

[The CyberPoet]

Here's possibly/probably what's happening:

The fueling is off, so the fuel-air mix is off, and as a result, the spark plugs are fouling. Easy way to tell: change your spark plugs and check the old plugs for signs of fouling -- compare them to a spark plug chart, such as this one: NGK Spark Plug Comparison Chart

How to cure it:
If you have old gas (more than a month old), get rid of it. Put in fresh fuel. Clean out the carbs manually, or at minimum run a fuel-system cleaner though the bike's gas tank (Techron is my preferred type/brand).

Other possibilities (less likely, in order of likeliness IHMO):
(A) The fueling system isn't refilling the carbs at a high-enough rate to offset use. After ten minutes time, the carbs are starving for fuel. Possibilities include poor fuel line routing, a fuel filter not routed down-hill, build-up in the tank blocking the pick-up screen, partially clogged fuel-filter, partially defective petcock vacuum diaphram and/or defective vacuum hose to the petcock.
(B) The valves are out of adjustment/mis-adjusted. As the temp comes up after ten minutes of running, the growth in their length results in them being way out of range.
(C) Something in the electrical system is over-loaded (such as too high draw headlights); after ten minutes of running, the insulation on the wiring has softened due to wire-heating and you're getting a ground somewhere along the wires where it shouldn't happen.
(D) One or more of the pigtail connectors are borderline defective (contamination); as the connections get hot, the resistance is increasing at the connector, ruining the signal.
(E) The coils are borderline defective, with a break in one of the windings. As the windings get hot, the break is opening up (physically), ruining the continuity of one of the coils.

Cheers
=-= The CyberPoet

[BrysonK]

I pulled one plug yesterday quick, and no carbon build up or anything, just a little whiter than normal (lean)

[WildKat]

I had some of the same issues you are having, last summer.. got the carbs cleaned, new plugs, and viola!! Havent had a problem since.. and an FYI, mine problem pretty much snuck up on me, similar to yours.. Its running fine, and within a few days, its so bad it barely starts when its cold and bogged down tremendously.

[BrysonK]

After some more riding, it seems to bog right out (like it has no fuel amost) at very close time periods (ie every 3-4 minutes) so im pretty sure its a fuel problem, any help?

[BrysonK]

lines are OK, and the tank is clean, pick up is clean btw.

When i take the petcock out, and look in the side of it (throu the nipples), and move the petcock to different positions, it doesnt move inside.

[The CyberPoet]

lines are OK, and the tank is clean, pick up is clean btw.

When i take the petcock out, and look in the side of it (throu the nipples), and move the petcock to different positions, it doesnt move inside.

The rotary selector knob switches between two pick-ups (one for reserve, also used for prime, and one for the ON position).
Aside from that, there is a vaccum diaphram that is spring loaded to push it shut, and vacuum-activated to pull it open (applies when in RES and ON; prime bypasses the diaphram). If the engine vacuum isn't sufficient, or the diaphram isn't air tight anymore, the diaphram won't open sufficiently and flow of fuel will be either less than ideal or zero.

Easy way to test: Place bike in PRIME when you go to start it and leave it there for testing -- does the problem go away? If so, get a petcock rebuild kit or replace the petcock.
Remember to switch it back to ON or RES when you shut the engine off to keep the carbs from getting fuel when the bike isn't running (avoids possible issues with flooding the cylinders and/or airbox).

Cheers
=-= The CyberPoet

[BrysonK]

Update:

After replacing the snapped throttle cable, i did some test drives with it on PRIME. Didn't bog down once/easier starting, and didnt stall out while riding. I tested it hot/cold and for different time lengths, and no symptoms of before. I thought maybe i had some gummed up carbs that got cleaned out, or poor fuel, but i decided to switch it back to ON anyway to see if there was a change, and sure enough, after 3-4 minutes of riding it, it bogged down and stalled. Switched it back to PRIME, and it started up after a bit and ran great after.

So.. defaultive Petcock? Heh..

Whats the harm in leaving it in Prime until a new one arrives? Is a faulty petcock a common occurance?


Thanks
BK

[The CyberPoet]

So.. defaultive Petcock? Heh..

Either defective petcock or defective vacuum line to the petcock...

Whats the harm in leaving it in Prime until a new one arrives?

Only when you park it. Switch it back to ON when parking, back to PRIME when riding. This will keep the carb bowls from accidentally flooding while parked (something that should only happen with a bad float mechanism, but better safe than sorry).

Is a faulty petcock a common occurance?

As the bike ages, yes. Few post-98 bikes have the problem, but it's quite common on those from the early 90's. Happens more often on bikes that sat without fuel in the tank (or where there was water in the bottom), but sooner or later the VOC's dry out, the rubber stops being flexible, and it simply stops working ideally. Cheap enough to fix or replace

Cheers
=-= The CyberPoet

[BrysonK]

Cool, Thanks. Yup, i change it back to ON when its parked. I dont think the vac line is bad, via visual inspection. I can replace it with a fresh peice to find out easy enough though.

Thanks again all.

[DreKat]

there could also be moisture in the airbox. I had that problem myself.

[mike10562004]

same problem here