Runs bad once hot

[HondaGuy]

Alright guys I'm out of ideas. I'm putting my friends 99 back into service after a long storage, and I've been through pretty much the whole bike. I overhauled the carbs, put in a new fuel pump and filter, cleaned all chassis grounds, eliminated the stator plug, have the regulator-rectifier feeding directly to the battery for power and ground with an inline fuse, did the crimp fix, have high 12 voltage at idle, just a hair over 14 at 2500 rpm, new battery, valves adjusted, and all of the chassis parts dialed in.

The problem happens when I go to ride the bike. It idles good and will rev to the moon when its cold, but once I'm about a mile down the road, the bike starts to break up and miss at part throttle, but it pulls like a monster past about half throttle. By the time im around the block, the bike will no longer idle on own and has to have the throttle cracked open to stay running.

I'm wondering if this isn't a coil on it's way out, but I feel like it would still run with one bad coil. What are the odds multiple coils are going bad at the same time?

For what worit's worth, mixture screws are about 3 turns out, carb synch is close, not perfect. No sense in doing that if it won't stay running.

 

[fmcandrew]

I don't think it's electrical if it runs fine when on the gas (but anything is possible)...sounds more like a jetting issue...pilots to be specific...major question: Do you need to choke it when cold to fire it?

 

[HondaGuy]

I don't think it's electrical if it runs fine when on the gas (but anything is possible)...sounds more like a jetting issue...pilots to be specific...major question: Do you need to choke it when cold to fire it?

It will sputter a bit without the choke when cold, but it wont really fire without it. After maybe a minute or so of half choke, I turn the choke off and it'll settle into idle around 1000 rpm with no choke. It'll idle there all day until I go to ride it. It's not till I get to the end of my 1/4 mile street that it starts acting up.

For what its worth, I just pulled the plugs and they're alll fairly white. This is after it sputtered out pulling back into my driveway.

 

[HondaGuy]

I cant see how it could be pilots. I pulled them out and very thoroughly cleaned them. But I guess with white plugs, it really sounds like a fueling issue. I'm just confused how it will idle so nice when cold. I even went through and checked all of the carb insulators with wd40 spray and rechecked the clamps once warm. No leaks.

 

[HondaGuy]

Ya know the more I think about it, the more it sounds like dirty pilots. The hot symptoms sound right just like dirty pilots. Wont idle, needs choke or throttle to stay running, idle screw adjusted so high it causes rpms to fall slowly, runs great once into main circuit. I just dont understand how it idles ok when its cold

 

[sdt354]

I've got a premonition that possibly the charging system/battery isn't up to snuff at idle. Can you hook up a voltmeter to verify? Are you using a charger when the bike is parked?
Steve

 

[HondaGuy]

I've got a premonition that possibly the charging system/battery isn't up to snuff at idle. Can you hook up a voltmeter to verify? Are you using a charger when the bike is parked?
Steve

The battery is brand new. At idle the bike fluctuates between 12.6-13.5, just because of the erratic idle. At 2500 rpm, it makes 14.1.

 

[fmcandrew]

I always shoot for cardboard colored tan...white/white is a lean condition...so, not enough fuel OR too much air...have you checked for leaks around the boots? Only true way to know is to stick a sniffer up the pipe and get readings at various throttle positions...plug reading is not an exact science...but it can get you close

 

[HondaGuy]

Well lesson learned, dont forget to pull the mixture screws out when you clean the carbs. I pulled the whole mess out this morning, and 3 out of 4 pilot jets are totally blocked. My guess is when I turned the mixture screws, all kinds of crud dislodged and blocked them up. Still not sure why it ran nice when it was cold, but I'm fairly certain this was the problem.

 

[D-Max2012]

Well lesson learned, dont forget to pull the mixture screws out when you clean the carbs. I pulled the whole mess out this morning, and 3 out of 4 pilot jets are totally blocked. My guess is when I turned the mixture screws, all kinds of crud dislodged and blocked them up. Still not sure why it ran nice when it was cold, but I'm fairly certain this was the problem.

OK, so now the question is, now that you've found some blockage and cleared it, is it still doing the same thing as before the blockage was found?

I asked this because I had a issue were my pulser pickup coil was starting to fail.
All 4 plugs were light tan in color. As per the plug reading area and the guys on the forum, that was were they needed to be. Synced carbs, looked to be dead on point once completed.
Fully broke down carbs and Ultra-Sonic cleaned them, 4 times until solution was clear.
Also, coated my tank to kill any rust / particle buildup from Ethanol fuels and water absorption with the air. Idle set to 1100 RPM. Got 13.6v - 14.8v on the meter depending on throttle.

Pulser Pickup Symptoms:
When the bike was cool, it would fire up without a problem with a little choke, then closed off the chose once warmed up a touch.
Bike would idle fine as the temp reached around 3:00 on the dial. As the temp reached around 2:30 and the fan kicked in, I'd notice that it would start sounding rougher and rougher.
It started to buck and pop while idling until it go so rough that the engine would stall.

After this point, it would not fire up again, even if jumped from my car. I knew it would not be a charging / battery issue once connected to that big car battery.

If I let it sit for a few hours to cool off, it would fire back up, and run normal until the temps rose again.

I took notes as to the intensity of the spark when the bike was cool.. It was somewhat visible in the sunlight. Once the bike warmed up, you could not see a spark at all.

Once I changed my pulser pickup coil, all sparks were BRIGHT in the sunlight, even after running for two hours AFTER my fan kicked in.

It's been running great since then..


Hope this helps you diagnose your issue.

 

[HondaGuy]

OK, so now the question is, now that you've found some blockage and cleared it, is it still doing the same thing as before the blockage was found?

I asked this because I had a issue were my pulser pickup coil was starting to fail.
All 4 plugs were light tan in color. As per the plug reading area and the guys on the forum, that was were they needed to be. Synced carbs, looked to be dead on point once completed.
Fully broke down carbs and Ultra-Sonic cleaned them, 4 times until solution was clear.
Also, coated my tank to kill any rust / particle buildup from Ethanol fuels and water absorption with the air. Idle set to 1100 RPM. Got 13.6v - 14.8v on the meter depending on throttle.

Pulser Pickup Symptoms:
When the bike was cool, it would fire up without a problem with a little choke, then closed off the chose once warmed up a touch.
Bike would idle fine as the temp reached around 3:00 on the dial. As the temp reached around 2:30 and the fan kicked in, I'd notice that it would start sounding rougher and rougher.
It started to buck and pop while idling until it go so rough that the engine would stall.

After this point, it would not fire up again, even if jumped from my car. I knew it would not be a charging / battery issue once connected to that big car battery.

If I let it sit for a few hours to cool off, it would fire back up, and run normal until the temps rose again.

I took notes as to the intensity of the spark when the bike was cool.. It was somewhat visible in the sunlight. Once the bike warmed up, you could not see a spark at all.

Once I changed my pulser pickup coil, all sparks were BRIGHT in the sunlight, even after running for two hours AFTER my fan kicked in.

It's been running great since then..


Hope this helps you diagnose your issue.

That is the next stop on my checklist if this carb issue doesn't clear it up. I wont know for sure till this weekend when my parts come in. Some of the mixture o rings were dry rotted, and I dont want to put them back in. I'll be sure to post the results either way.

 

[fmcandrew]

Hopefully it works out and hopefully you don't need to spend $$$ on electrical parts...

 

[HondaGuy]

I really thought I had it nailed when I solved the charging issue. This bike has honestly had more problems than anything I've ever worked on. We trailored it to my house, and the forks immediately puked all over my floor. Then the valves were all on the tight side of spec. Then the calipers started leaking. Figured I'd rebuild the carbs since it sat for a few years, and found all of the intake boots dry rotted. Next the clutch slave cylinder blew out the seal, so rebuilt that, so of course the reservoir gasket would leak after that was fixed. Then the not charging fiasco. And if course the fuel pump was completely dead, so got creative and put a low pressure Holley pump in. Found tubes inside of the bald tires, that was unexpected.

I cant wait to get this thing out of my garage!

 

[HondaGuy]

All of the issues I've encountered all stem from this being ridden hard and put away wet. I dont think it ever got any service besides oil and tires. I've had 40 year old bikes that were in better shape than this one was. No doubt this thing would have been parted out if it went anywhere else.

 

[HondaGuy]

Alright guys I finally got it. The bike runs great. I just took it for an hour ride and it fell right into idle at 1000 rpm at every light and ran smooth through the whole rpm range. The problem was the pilot jets. It was my mistake not pulling the mixture screws out when I cleaned them the first time, and it dislodged a bunch of crud when I adjusted them.

By the way, I picked up over 2 volts at idle by doing the crimp fix and feeding the regulator directly to the battery, but that was before I did the carbs the second time. If anybody is having charging issues, that's a great place to look.

This isn't a bike i would normally ride, but my friend needed some help and you don't really have to twist my arm to get me to swing some wrenches. I gotta say this bike makes my old CB750, GL1000 and GL1100 seem like slow dinosaurs, and the Kerker 4 into 1 sounds incredible. Just a little too loud for my taste.

Thank you all for all of your suggestions and help!

 

[D-Max2012]

Glad you got it ironed out buddy.. Great perseverance.

 

[fmcandrew]

Glad you got it sorted...now you can enjoy the fruits of your labor!!

 

[D-Max2012]

Now that you've got your buddy's bike running right, you have to convince him to let you ride it every weekend.. Before you know it, you'll be picking one up for yourself.. lol!!

That V-Max venom, lasts a long time after you've been bitten.
It got me when I was 17 and it stayed in my system till 5 years ago.. I'm 52 now :rofl_200: