Power loss, idle drop.

OK, braintrust, here's my circumstance: Started up my '97 to leave work, running fine, idling to get out of parking lot. Like flipping a switch, rpm drops from 1400 to about 1000, go to take off, not much power at all. No missing, popping or sputtering on accel or deaccel. All four cylinders are firing, (burned finger test). Made it home, idles fine, just lower. Any direction what to look at first? Sounds/feels like a fueling related issue to me.
Many thanks in advance.

 

It sounds like the ignition timing somehow retarded itself by 5 to 10 degrees... I don't know 4th Gens at all, so i have no idea what controls the ignition timing. If it is fuel related, I would think that it wouldn't have gotten you home (depending on the length of the trip), and the immediate drop in idle speed/power output with no misfiring doesn't sound like fueling issues. Not that ii isn't; it just sounds more like a timing problem.

 

Pull the plugs and have a look, sounds like ass-gas to me.

 

Hmmm timing, I'll check it when I can work on it this weekend. I did pull the plugs, dark brown even with the Staintune, but I live at 5500 ft. Thanks for the input.

 

Has it gotten colder recently? I notice with all my bikes that they idle lower when the temp drops a few degrees. If this is it just adjust the idle speed.

 

Spark timing is built into the CDI box, and i don't believe that it can ever go out of whack as long as the box is capable of sending its pulses.

I'd guess a partial clog in one of your idle jets, but some slow speed riding and a plug check might locate your problem.

Yes, cold temps will affect idle speed.

 

Thanks everybody for your input. Yes, Mr. Squirrelman, I do believe I have a clogged jet in one of them and they are coming off and apart tomorrow. It idles fine but I can tell it's not right, rev it up to 2500/3000 and it pops and burrbles a bunch. It will rev, but not as willingly as normal. I haven't touched the carbs in over 3 years, guess it's about time. Only problem is I had a ride planned to go up north this weekend-the weather is beautiful here. Oh well. :frown:

 

Before you dive into the carbs, i'd suggest trying a can of SeaFoam first since your problem is not too severe, and it might possibly work and save you lots of time if it does.

 

Fresh gas, dose of Seafoam, 25 mile ride = nada. Added more gas, Seafoam and Chevron Techron +2 concentrate, 25 mile ride = nada. I've used it before, really hoped it would work this time, no joy. Oh well, it's been 3 years since they were off, guess its time to see what they look like now. It's been 2 years since all the gas in this area went to the corn fluid garbage so it will be interesting to see what they look like compared to when we had real gas. Thanks for the input, I appreciate it.:smile:

 

I had mine off after 21 years! They looked mint, fer real. There was maybe a tiny tiny blob of black shate on the bottom of one of the bowls. I was thoroughly impressed! Anyway, why dont you unscrew your fuel mixture screws, you have the needle jet, then a metal washer, then a rubber o-ring. Take this out in this order, one at a time and spray some carb cleaner in there with some air. See where that leaves you.

I had problems with a low speed stumble before I did a major carb service and used some BG-Carb shit introduced into the fuel rail without any results. When I did the needle jet tune up it cured it! I would not discourage you from tearing into the carbs as it brings you closer to your machine, we know how that feels :smile: I did replace the bowl gaskets along with the needle jet 0-rings which you have to buy as entire part from Honda. I am not afraid to spend money on my shit though, if you look at it from a point of view where a new bike is gona set you back $13,000 its cheap. Anyway, good luck... Ass-Gass sux :sad:

 

What kind of gas do they have in your area? The 10% Ethanol crap is year round here now. I'll post up what I find, this is the first time I've done 'em, the guy I bought it off of 3 years ago had 'em done by the local dealer because it sat so long. (It's a '97-I bought it in '08-it had 3900 miles on it)

 

Had to go in to work today for a 1/2 day, so I only just got it all back together and took it for a short ride. Basically all I did was punch a wire through the jets after removing them, blew WD40 through the openings, cleaned everything best I could in the time I had, set the mixture screws to 1 1/2 turns out ( I live at 5500 ft. ASL) put it all back together and fired it up. Result: will idle no problem as low as 750-800 RPM, take throttle perfectly, revs great, no popping, spitting, drama on accel, steady throttle or de accel. Will burn through the last of the Seafoam/Techron gas tomorrow on the way to work and throw some Chevron 88 in it. Thanks for all the input.

 

Happy Endings are nice...

 

Glad it was an easy fix. :smile:

I'm curious; in your original post, you said "No missing, popping or sputtering on accel or deaccel." In a follow up, it was "rev it up to 2500/3000 and it pops and burrbles a bunch. It will rev, but not as willingly as normal." Did that change from when you originally posted?

 

Yes, Sir. All I can figure is the Seafoam loosened up something in the low speed circuit to cause it, because it's back to doing it again. Rode it to work on Monday, ran great all the way there and ALMOST all the way home. Sitting at a light, the idle dropped again-this time only about 200/250 rpm. It'll take gas/rev, but not quickly and not a lot of power. Put some fresh Chevron 88 in it last night and rode it to work (30 mile round trip) today-same symptoms. So I guess the carbs come off and I'll hit the low speed circut again. Above 5000 it pulls like a train. (love that sound, it has a Staintune high-mount on it)

 

When you work on them next time, take time to buy actual carburator cleaner, I used this Chem-something or other, white can with red and blue on it. Could go the Gum-Out direction too, use some safety glasses as getting this shit in your eyes stings. Take your time and use compressed air to blow out what your working on... Gud LuK + keep us posted

 

^ Probably "Berrymans Chemtool"; it's been around forever. It is quite happy to destroy anything that is non-metallic, just FWIW. It will not remove corrosion of any kind, just sludge and varnish. The most problematic carbs I've dealt with are the ones that have corrosion in the cross-drilled passages.

Hopefully you just have some crud in the float bowls or fuel lines that is breaking loose and causing problems.

 

Yah - Dats dah Shit, Chem-tool by Berryman...I have used Top-Job as well as purple stuff to clean carbs :smile:

 

That bike sat along time. Check for rust in the tank. (Use a flashlight not a match) You might need some fuel filter work. Also, I don't know how air gets back in that model's tank but next time it does it try popping the gas cap open and see what happens.

 

Have you inspected your plugs ?? At this point i'ts important to check plugs and see if you can locate one that's misfiring, cuz it seems like you're losing one cylinder, and that's dragging down the idle speed.

Might be a good time to replace all 4 plugs if they don't look good.