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Discussion Starter · #1 ·
Hi folks, a newbie to actually posting, but I've been trolling since I got my'98 916 almost 2 years ago. The bike has been a crazy pleasure, I have several sixties Hondas that I've restored, and while I love those things (and my BMW 1150RS for going farther away), the 916 has been a long lusted for bike and the experience has lived up to the anticipation. The bike has low miles on it, a little over 7k, 2k of which came during my ownership. The PO had just had the valve and belts done prior to purchase (came with reciepts), so at least during his tenure, it seemed to have been well maintained. The first owner was Mike Tyson (!), I have a color copy of the Nevada title, who had had the body work sprayed flat white!! It appears that Iron Mike didn't ride it much, must have been a trophy in the garage. The PO had returned it to it's native red (thus the slight shade difference w/ the tank), but I recently decided i needed to take things a up a notch and clean up some of the flat white overspray and put on some bling and better parts. So I picked up some carbon - airbox, intakes, front fender, rear tire hugger, etc. as well as some new stainless brake and clutch lines, and to filter the incoming air now that the former inline air filters were gone, some PiperX air filters. all these were put on successfully - a bit of a struggle w/ the PiperX filters - and the bike looked much better.
The first rides after the work, everything seemed fine. Very soon, I started getting some intermittent stumbling in the idle at stops that could be cleared with some application of throttle. This has gotten more pronounced recently, with stumbling and running on a single cylinder even while at speed. I obviously disturbed the whole fuel take and hoses during the installation of the airbox and intakes, I'm guessing that the fuel filter and associated plumbing is likely the first place to start. Any other hints, suggestions and directions would be greatly appreciated. It's highly depressing to take such a fine running beast and unintentionally wack it while doing mostly cosmetic stuff!

Thanks for your help!

Jack
 

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I'd start by re-tracing your work. You could have disrupted a wire or pinched one of the fuel lines. Most likely it's something simple since the bike worked fine before the mod's and now doesn't. The moment you start going in another direction like replacing the fuel filter, you will be disrupting another part and adding more complication. So pull it back apart again and re-check your work, I have a feeling you'll find the problem right quick.
 

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Nice bike. I like how the previous owner went back to the Cagiva decals. Although I agree with Tuned's approach, it may very well be a coincidence that the issue started shortly after the mods. While you have the fairings off, you may want to also take a look at the connector to the regulator/rectifier. They are prone to melting and shorting. The rectifier itself may be going bad. You may want to have it tested. Good luck.
 

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Discussion Starter · #4 ·
Thanks for the direction and encouragement guys, I'm sorry that this response is slow, I need to try and get some notification that there's been a response (that and some time to get back to the forum - work impeding motorcycle time...). I agree that goinng back into the airbox to look at what's going on is the correct start, hopefully it will be obvious since I'm less comfortable sleuthing out issues with this bike than I am with my old Hondas - I guess its time tho!
The previous owner replaced the R/R so hopefully that's good but I'll definitely keep that in mind if I have to go beyond the obvious. I'll let you know how it goes once work and travel let me get back to it!

Thanks,
Jack
 

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Discussion Starter · #5 ·
Back to the unhappy 916

Ok -
It's been quite awhile since I left this thread dangling, but life interceded, so finally I was able to dig into the the thing to see if I could sleuth out why the bike was running so poorly. I pulled the bodywork and reviewed the state of things as I left them. I could not see anything that should have had any effect n the bike's operation, short of the effect of the Pipercross filters in the airbox, see the first figure below. They take up a lot of the airbox volume, so I don't know what this effect would be but it's hard for me to imagine that this would cumulatively cause the bike to run progressively worse - it should have run bad right after I put everything together following the work. I gave up the what else could I have done investigation and decided to move on to seeing what I might have done to the tank.
This was much more illuminating, after pulling out the pump unit, I could see trash at the bottom of the pump inlet. I pulled the pump out, and the cavity below the pump was full of crud, very bad (see pic). Further, when I pulled the filter and poured the gas out the reverse direction, it was brown sludge - obviously nothing had ever been changed, the clamps were original. Looking for the source of all this crap, I found that the tank lining was starting to separate in a number of spots, and all the lining on the lower flat portions of the tanks were gone, with corrosion starting. Not ready to try and strip the interior lining and recoat at this juncture, I removed the loose lining, swirled solvent in the remaining tanks and brushed the loose corrosion and then drained the solvent, rinse repeat. Got it much cleaner. Cleaned the pump housing of its crud, replaced the filter and reassembled. I also replaced the plugs (old) and the plug leads.
Feeling much better about everything, I started the bike back up, and for a brief moment, it sounded like it was it's old self, then it got progressively worse to the point that all I can say as it's certainly no better, it might be worse, certainly not rideable. Shit!
So its' back to the drawing board. I think that the fuel situation is better (not saying much), the fuel I drained before starting had a lot of crud in it, and inspection of the fuel from the filler neck with a flashlight shows everything is much cleaner. Suggestions from anyone dealing with a de-laminating tank liner - as far as removing the remaining liner (I've lined several old Honda tanks in the past, never had to remove old liner tho), would be appreciated. Since the idle is down to 1000 RPM and lower, stumbling, and uneven acceleration as RPM is increased, any other things to try to suss out the source of the poor running will be even more appreciated (I haven't looked at the regulator yet but that is on the list). Spring is here in VA, and the bike is unhappy, so I'm unhappy! Help!
 

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Hmm… how about the pump itself? It does sound like something is "going bad" when it runs for a few moments, so that type of intermittency could be simply a bad pump. I'd also yank the injectors out of the throttle bodies and clean them in an ultrasonic cleaner. Do a google search to find out what cleaning solution to run. But that will clean out any crud that got through your fuel system.
 

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I agree that the injectors may need cleaning.
What kind of cleaning solution do you recommend? I've always wanted to know because I usually bring my injectors to a friends place and clean them in their ultrasonic cleaner.
 

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What kind of cleaning solution do you recommend? I've always wanted to know because I usually bring my injectors to a friends place and clean them in their ultrasonic cleaner.
In this instance, cleaning with ultrasound is the preferred solution.

Gasoline is itself a solvent that is formulated with detergents to keep your injectors and fuel system clean under normal driving conditions. However when you shut your engine off, fuel system components that see direct heat from the engine, bake the fuel causing buildups of waxy, tar-like deposits. When you restart, the gasoline again acts like a solvent for these deposits but over time they can build up, especially if you tend to take mostly short trips. After about five years/50,000 miles they say that you can expect your injectors to be 10-20% clogged, even if you regularly add an injector cleaner to your fuel. Deposits elsewhere, such as in the throttle bodies, is usually of no concern unless they cause some sticking of the butterflies.

The tiny orifice of a fuel injector nozzle is the most susceptible to fuel system buildups and contaminants such as rust or fuel line particles that make it past your fuel filter or are introduced during repairs. The injectors always have to be removed in order to remove any foreign bodies. Such injectors dribble fuel out, and show asymmetrical spray patterns that reduces fuel vaporization and consequently engine power. An injector should spray a fine mist.

Injector cleaners contain chemicals such as toluene (normally found in gasoline at lower concentrations) that need to be diluted with fuel to avoid damaging fuel hoses and o-rings. So, even if used regularly, these cleaners won't remove tough deposits in low-flow areas. Further, these cleaners can damage expensive oxygen sensors and catalytic converters. Professional cleaning services remove the nozzles and use ultrasound equipment to scrub the deposits off. This technique vibrates the injector (while it pulses) with ultrasound waves that then breaks up the accumulated deposits.

The most common problem with injectors is they accumulate a buildup of inside the injector and on the pintle/seat area. The injectors are manufactured to such close tolerances that a 5-micron buildup (a human hair measures about 70 microns) will reduce the flow up to 25%.
 

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Discussion Starter · #10 ·
Frustration builds

Well, first of all, thanks to all for the suggestions, I had to agree that the injections were likely polluted given the quantity of crud that I found in the tank and the old filter. Sure enough, when pulled, they looked bad, with a nice thick ring of brown rust sludge in the injectors little cubby inside the throttle body. I cleaned that out, there is some evidence of oxidation on the throttle body underneath the sludge which i didn't do anything to except clean thoroughly. The injectors themselves were pretty bad shape, and while I was looking for a ultrasonic cleaner and new o rings, I came across a pair of NOS injectors from Ferraci that I went ahead and bought, with the old ones as backups. Got everything installed and big drumroll..... Crap! not one bit better! Some observations that that may help - when it first starts, it runs relatively smoothly, with a stable idle around 1300 - 1400, and will rev with few stumbles. As it starts to warm up though, the idle starts to drop down to closer to 1000 RPM, and the stumbling increases, such that advancing the throttle quickly from the low idle will sometimes kill the engine. As it gets warmer, the bike pops and misses even at the higher RPMs. It seems like it's running lean as it warms up.
Well, I didn't replace the fuel lines or the fuel pump, it makes it's little whine on startup for a few seconds like it always has, so I don't know if there's reason to replace that, even though it has obviously been pumping some pretty crappy stuff. I have to think that there is something fairly wrong with the mixture, given it's variation as the engine warms - it would seem unlikely that anything electrical would have such an effect. I'm starting to wonder if there is something going on with the ECU that just coincidentally started some point after it changed out the airbox.
I do not want to admit defeat and lug the damn thing to the dealer and get raped (and have them hang on to it for over a month like the last time it went there), but some of the best riding weather is passing me by.
Again, thanks for the suggestions and commiseration
Jack
 

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Discussion Starter · #11 ·
Well,
A final followup - after consideration, I felt that the only thing that I hadn't replaced was the fuel pump, so I got one of the replacements off of ebay, a little nervous about the selection but it turned out fine, an exact duplicate of the original. After pulling and testing the original and comparing with the new one, it became obvious that even though the old one was running, there was no air coming out when running the until outside the tank, vs. the new one putting out a nice stream of air. put in new metal quick disconnects as well as all new fuel line to be sure, and hot damn, the bike runs like a beast again, even smoother during constant low speed running that had always been somewhat uneven since I got the bike. Yay! Just went out for the inaugural run and after a big yank after the light turned green, the tranny locked up in second! Time for a new thread after I do a search.
Thanks for everyone's help

Jack
 
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