Intermittent Power Loss - Suggestions?

[eschie]

Hi all! New rider here, first month riding with no maintenance experience.

I began losing throttle power going ~70mph, then my bike died. Had issues starting up then throttle would become intermittently unresponsive, especially if I rolled on too quickly. Got it running on RES and rode home in low gears.

I've read a few posts saying to check spark plugs after running for indications, vacuum check hoses for leaks, and then clean and balance carbs.

I'm off now to ride it a bit to try and replicate, then check the plugs before and after.

What's my next move? Why would the bike die on ON but not RES?


Background info:
'05 250r (salvaged)
5200 miles
Daily commute ~25mi. round trip. (up to 85mph with ease)
Laid it down a week ago (right side) at 10-15mph and ran fine.
Idle issues only when cold (idle fluctuates and sometimes dies w/out throttle), and maybe happened warm once or twice.

Long Story:
I was riding home from work yesterday going ~60-70mph when I thought I noticed the bike not going as fast as it should be given my throttle application. (I remember thinking, this headwind must be crazy!)
A few minutes later, I noticed my throttle suddenly lost some power and for just a few seconds, the bike lagged and jumped, then went back to normal.
Another few minutes later, I slowed down to go through the toll and thought I heard my engine bogging for a split second, but again couldn't tell due to the wind.
As I made my way onto the Bay Bridge, the throttle lost power again, but this time the rpms dropped to 0 and the engine died.
Luckily I was in the left lane so I pulled over onto the shoulder.

For about 5 minutes, the bike wouldn't start without at least half choke, and would die the moment I gave it throttle (if I managed to get it within idle range).
I finally got it started again with choke and attempted to ride off while adjusting it.
5 minutes later it died again and I was on the shoulder.
A fellow rider saw me ad came to help me out: I wasn't low on gas, nothing was dripping from the bike, and the throttle cable was functioning properly.
On his recommendation (thanks Ebby), I switch the petcock to RES and kept it in low gear until I reached Moto Guild on Treasure Island.
There, the owner helped me look it over: oil seemed fine, I tightened the leads on my battery just in case, and it started up without issue on RES.
The only weird thing was when the bike was started on its side stand, it idled fine. But when I stood it up between my legs and swayed it side to side, the engine puttered a bit. It reminded me of when I start it cold, how the idle fluctuates and sometimes dies w/out throttle.
He recommended I ride it around the island a bit before trying to ride it home.
So while running from RES fine, I switched the petcock back to ON and made my way back to the bridge.
Just before getting there it stalled and died again, this time at a relatively low speed (2nd/3rd gear).
This time, I adjusted the idle speed to just under 1500, switched back to RES, rode it around for about 20 minutes before riding home in 2nd/3rd gear with no problem.

[Triple Jim]

Is there an inline fuel filter? I added one to my 250, and although it looked fine, it clogged last week and I got some of the symptoms you described (not all). I consider the clogged filter to be a very good thing, since the junk that clogged it would have otherwise gone into the carbs!

[eschie]

Originally Posted by Triple Jim

Is there an inline fuel filter? I added one to my 250, and although it looked fine, it clogged last week and I got some of the symptoms you described (not all). I consider the clogged filter to be a very good thing, since the junk that clogged it would have otherwise gone into the carbs!

Hey Jim. It does not have an inline filter. I do plan to install one after I clean the carbs.

Today I'm going to pull the carbs and inspect the OEM filter. If they are nasty will clean them on Monday.

[Triple Jim]

I'm not aware of any OEM filter in the pregens, but I don't know everything about them.

[Ghostt]

It could be vapor locking issue, take for a test ride again, when it dies again, open the fuel cap, pay attention if there's any noises, and then try to start it again.

Let us know if this works or not, as this is a common problem.

[Triple Jim]

Good thinking, Ghostt. Although a clogged filter turned out the be the cause of my recent troubles, before I figured that out I disassembled my pregen's gas cap and found the labyrinth of passages that make the air vent system were nearly blocked with corrosion and goo. I'm sure I prevented a future problem by cleaning it.

[Ghostt]

Thats why I recommend doing the fuel cap mod, I consider it preventive maintenance.

Also PreGen doesn't have a fuel filter, adding an in line filter is also a preventive maintenance step as well.

Here's my write-up on the subject,

Sounds like it could be a venting issue, no worries it's a free and easy fix,

You need you to disassemble the gas cap and remove the two small red diaphragms, assuming this is your only problem.

The diaphragm gets hard and losses it's flexibility and gets stuck, and doesn't allow proper venting.

IMHO this modification should be done regardless to prevent future problems whatsoever.

They are ment to vent the tank, but in the case of an accident not allow gas to leak out, but more often cause problems then they fix.

Here are some pictures to help you.

The plastic piece houses the two small red diaphragm pieces, this one being mine, they are already gone, and you can leave the plastic piece out all together, as I'm going to do now.

Some things to watch out for are, there are 5 small springs under the round collar, and a small round collar as well on the locking mechanism, don't lose any of them.

Good luck.

[eschie]

Originally Posted by Ghostt

It could be vapor locking issue, take for a test ride again, when it dies again, open the fuel cap, pay attention if there's any noises, and then try to start it again.

Let us know if this works or not, as this is a common problem.

So I just took it out for a short ride. It started up normally on the first try with minimal choke application on RES. I rode it around the block no problem. With the bike still running, I switched the petcock to ON and tried to do the same. The first few stops were fine, but then it died on the last stop. I started it up again easy, but then it died shortly after throttle application. Started it up again then died without throttle. Eventually fighting with the choke I could not get it to idle as the second I got it steady anywhere below 3k, the rpms would immediately drop to 0.

When opening the gas cap I notice a small amount of pressurized gas escaping. I'm unsure if the bike was more likely to start after opening the gas cap, as each successive try made it more difficult to start up.

Also, I noticed on starting the engine the headlight was going out and I cannot recall if this is normal behavior.

[Triple Jim]

Your petcock may have a clogged passage in the "ON" circuit.

[Ghostt]

Okay so do the gas cap mod, per my write-up, also check the fuel shut off valve / petcock for proper operation, if not try disassemble the petcock, you might need a new one.

If your petcock is shot, save your time, and money and get a new one, the cost of rebuilding it isn't much cheaper, due to you need two separate kits, as they for some reason don't make just one.

New one cost about $65.00

1988~00 models
http://www.partzilla.com/parts/detai...1023-1139.html

2001~07 models
http://www.partzilla.com/parts/detai...1023-1393.html

Also be sure to order the orings(92022-183 WASHER,6.2X11X1.5)and new bolts(92001-1091BOLT,6X20),trust me you'll be better off in the long run.

Rebuilding kits are about $60 total.

K&L Supply Diaphragm Only for Fuel Petcock Repair Kit 18-6638 https://www.amazon.com/dp/B0055DWO60..._s1CGub1W9N3PH

K&L Supply Fuel Petcock Repair Kit 18-2723 https://www.amazon.com/dp/B001KO2JRW..._U1CGub05DT5NT

http://faq.ninja250.org/wiki/Rebuild...tcock/fuel_tap

IMHO not worth it rebuilding, also be sure to check vacuum and fuel lines for wear, holes, and cracks, if in doubt replace them. Also replace the two small O-rings on the bolts for the petcock part# 92022.

This is the time to add an inline filter filter, if you don't have one already.

K&N 81-0221 Fuel Filter https://www.amazon.com/dp/B000E2AR70..._ncMwwbE333H0E