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Koch's Carburetor Rebuild Photo How-To| Return To MagSab High Tech & Customization Site Main Page |
The Carburetor Page |
Topics:
Installing Those
Pesky Carburetors!! Dial a Jet Kit (7-17-99)
References:
Cliff
Koch's Carburetor Rebuild Photo How-To
Contents (This Page):
Carburetors / Gummed Up / Storage
Carburetors / Inspection, Removal
Sticky Sliders
Carburetor Related Hesitation
Carburetor Modifications / Jet Kits
Carburetors & Fuel Filter
Carburetor Problem & Diagnosis
Clogged up carburetors is a common ailment for any motorcycle, caused by long term storage without draining or treating the fuel. After three or four months, untreated fuel can go bad, gum things up, and make starting nearly impossible. As Tom F. has pointed out, in hot climates such as that of Arizona, fuel can evaporate and varnish carburetor guts in as little as a month or so. It's possible on occasion to start an unprepared vehicle that has been sitting for over six months, but don't count on it.
There are two common methods used prior to storage to eliminate the clogged carburetor dilemma. One method is to completely drain or burn all fuel from the tanks and carburetors. However, unless you coat the inside of the tanks and carburetors with oil, you may experience internal rusting and corrosion.
The other method of storage preparation, is to fill the tank with high octane fuel, add the correct amount of fuel stabilizer, and ride the bike for at least five minutes to ensure that the stabilizer has gotten well mixed throughout the system. Most stabilizers claim to treat fuel for only up to one year however.
I prefer the second method since it allows one to easily start, and take the bike out for a spin, even during it's storage period. When your done, the bike can be parked, and it's all ready to go back into storage. No need for re-draining the tank, etc.
It's a good idea to start up the engine every few months anyway, to keep the engine internals and seals lubricated. If possible, when starting the engine during storage, ride the bike until the engine gets good and hot. Merely starting the engine and letting it idle for 10 minutes during the winter will only help contaminate the crankcase and exhaust system with condensation, not allowing enough time and heat for the start-up condensation to burn away. Also, excessive idling is not good for the engine, period.
Removing the carburetors from the V65 is somewhat difficult and time consuming, because there is very little room to maneuver between the cylinders and frame. All four carburetors must be removed together as a unit. Do not try separating them during removal from the bike, or you will most likely damage the fragile shafts, linkages, and air/fuel joint pipes.
If you merely wish to take a peek at your carburetor internals without getting involved in a big project, it is possible to remove at least two of the carburetor bowl covers from the carburetors without removing the carburetors from the bike. Using a few good angled phillips screw drivers, drop the covers and inspect the float, jets, etc. Just remember that the idle/starter jets are not removable, regardless of what the manuals say.
If you remove the carburetor bowl covers, you may need to replace the gaskets. Most of the time the gaskets do NOT have to be replaced, but be prepared if they do!
Dave Miranda Reports:
Once, I had also witnessed success reusing old bowl gaskets. But twice, I have witnessed
failure and leaking fuel reusing old bowl gaskets. Fuel resistant gasket sealer helped for
only a little while, but then failed too. Since the bowl seam is covered in fuel all the
time, it's very hard to keep it tight. Most try to avoid having to get new bowl gaskets,
since you cannot just buy one without purchasing a whole "carburetor kit" from
Honda, which runs about $25 a carburetor. Four carburetors, you're looking at over $100
just for four little gaskets. Someone did once mention that there may be an after market
supplier of gaskets, but I have not researched this. Anyone out there know of anything? As
I see it, attempting to reuse bowl gaskets is a hit or miss proposition, and once you put
the carburetors back in the bike (which is a pain), you certainly don't want to have to
remove them again.
I have NEVER had this problem.
I have rebuilt my carburetors at least 7 times in the past 6 years. Once every
15,000 miles or so, or to put in a jet kit. Each time I reused the existing bowl
gaskets with no problems. Remember, however, I usually keep the bike in prime
condition, and use stabilizer, and keep it clean! Maybe that's the reason!
More incentive to keep up with maintenance!
If you suspect a sticky "slider" piston, or damaged diaphragm, the vacuum chamber covers (chrome caps at the top of the carburetors) can also be removed without removing the carburetors from the bike, though you'll need to remove the radiator. I find that the radiator is easier to remove than the carburetor cluster. When installing the sliders and diaphragms, it's very easy to allow the diaphragm edge to pop out of it's seat, which can then get crimped into the wrong position, allowing an air leak. Such a leak will cause poor performance, hesitation, etc. Some mechanics prefer to tack the edge of the diaphragm in place with a very tiny amount of gasket tack before installation. Be careful not to allow any carburetor cleaner to get on the diaphragms, as the cleaner will permanently deform the rubber. New ones cost about $65 at the discount places.
Bottom line, if performance is down, and you suspect that your carburetors need cleaning, don't hesitate (no pun intended) to remove them from the bike, and do a thorough cleaning job. If the carburetors indeed have collected gum/varnish, cleaning them will most likely make a very noticeable improvement in performance, and you'll be very glad you did it.
Merely pouring "carburetor cleaner" fuel additive into the tank may help over time in very mild situations, but will not clear up stubborn clogs. Dave M Has run many tank fulls of heavy-duty carburetor cleaner additives on a V45 that had gummed carburetors. After finally disassembling the carburetors, it was apparent that the degree of gum still present would have never disappeared without a full-scale internal cleaning.
Replace those stupid phillips head screws on his carburetors (carburetor to intake box screws, bowl attaching screws, etc.) with allen head screws, which will make future removal MUCH easier. The phillips head screws are often very difficult to remove, and "round-out" easily. McMaster Carr has a whole line of inexpensive, 316 stainless steel screws at really inexpensive prices. These bolts polish up nicely, and look almost as good as chrome! And you know how important that is!
Several V65 owners, and even more V45 owners, have complained of a hesitation somewhere mid powerband. Some have said that this "inherent flat spot" is caused by a carburetor system transition?
According to the MagSab sight, V65s, V45s, VF700s, indeed have an inherent midrange flat spot, caused by "EPA mandated carburetor resulting in too lean a mix in the midrange... more a problem with the V45s/VF700s." The problem can be corrected by raising the main needles, but they are not adjustable. The needles can be shimmed, but apparently not enough to make much a difference. "You might consider installing a Dynojet kit" in order to richen up the situation.
The point is, if you do experience a slight hesitation around 5,000 rpm or so, you're not the only one. My V65s don't seem to yield any annoying flat spots, though a few V45s I've ridden did have noticeably weak midrange zones. After studying horsepower/ torque curves of V65s as in the attached test articles, etc., I have noticed that the power does seem to climb upwards from 6,000 rpm. This rise in power may create a false feeling of a flat spot just before. Some torque/horsepower curves do actually show a small dip around the 5,000 rpm mark as well.
I owned a V45 Magna that had a terrible flat spot mid band. Shortly after, the carburetors were yanked, and a decent amount of gum/varnish was found and removed. After that, there was still bit of a flat spot, but not nearly as bad as before. These lean systems will be very sensitive to even the smallest degree of extra leaning caused by gum/ varnish deposits. If you experience an annoying flat spot, be sure the carburetor internals are truly clean before planning any carburetor modifications.
A common cause of hesitation is sticky vacuum pistons, and/or leaking piston diaphragms. Again, these can be checked without removing the entire carburetor block from the bike.
The 'flat spot' is not someone's imagination, and a lot has been written about it. In the future, this page will report on the various jet kits and other methods of dealing with it. To get more information on what people have done in the way of shims, see the MagSab FAQ or post a question to the MagSab List.
Many claim, especially with the later models, that low end performance can be improved by re-tuning the carburetor pilot screws. This involves removing the anti-tamper plugs, and adjusting. The official Honda manual gives instructions on how to adjust the pilot screws, using a typical lean drop method.
Some have told me that on later models, from the factory, only the pilot screw of carburetor #1 is adjusted properly, and the other 3 screws are adjusted very lean, in order to get the bikes to pass regulations. When I checked the pilot screws on my `85 Magna (which appeared to have never been tampered with), they were more or less in their optimum position, maybe just a bit lean. Regardless, especially if your carburetors have been rebuilt, modified, or tampered with, it's a good idea to re-adjust the pilot screws per the lean-drop method for accuracy.
As mentioned earlier, installation of a K+N Dynojet (Stage One) performance carburetor kit can help reduce any lean stumble created by the emissions conscious factory tuners. Tom F. tried a Dynojet kit, and a dyno test revealed that the kit produced 3 horsepower over stock at high rpm. Tom also notes better overall carburetion, but recommends that the kit, at about $90, is probably not worth installing unless you need to have your carburetors reworked anyway.
Keith M. installed a Stage One kit into his `83 V65 Magna, and reports snappier response, especially at lower speeds, which is "well worth the accompanying drop in gas mileage". Keith notes that both highway and city fuel mileage has dropped over 5 mpg since installation of the kit.
Gaylon G. has installed a Stage One kit into his `86 V65 Magna, and reports "slightly crisper throttle response".
Jeff D. has fitted a Stage One kit into his `85 V65 Magna, and reports "no noticeable difference".
If you feel your bike is running lean and lacks power, inspect your carburetor internals before ordering a jet kit. You may just need a good carburetor cleaning, and/or tune up.
For those who have installed a greater flowing exhaust
system, a Dynojet kit will probably make a more noticeable improvement than otherwise.
Be Careful, however. Do not use ONLY a brass element filter. The element is not fine enough to filter out all the crud.
I have rebuilt the carburetors numerous times, for general maintenance and putting in jet kits. Both the 1984 and 1986 took different kits, and the rebuild went extremely well. The carburetors were not dirty to begin with, I guess from all premium gas and riding year round. The stock phillips head bolts that held the carburetors to the aluminum air box bottom were almost impossible to remove. Even using WD-40 and an impact driver did not make it easy. To remedy this in the future, I replaced the stock screws with allen head screws. I was careful to choose bolts that would be corrosion free, such as the ones supplied by McMaster Carr. I did the same on most of the carburetor phillips head screws, such as the ones holding on the diaphragm covers, and the float bowls. This really helps if they ever need to be disassembled. When using the carburetor cleaner, I was careful not to use it on the vacuum diaphragms. I lost one that way. What happens is that most carburetor cleaners will soften and permanently deform the rubber. The cheapest price to replace them new that I've found is $65.00 each. Lucky I had a few spares.
Here Goes…(Addressed to the MagSab Group)
Okay, I knew It had to happen. I have a problem with the V65 that I am at a loss to diagnose. Last Friday night, the bike was running fine, and then, on the highway, I noticed it starting to bog. I thought that this was a momentary thing, but it turned out not to be. The bike idles OK, and revs OK at rest. When riding, at low RPM's, or not accelerating, it seems to be running fine. As soon as I give it gas, it bogs & sputters and does not accelerate correctly. It does accelerate, but that sort of "I'm only running on 2 or three cylinders" acceleration. I'd swear it was running on 2 or three cylinders. Once it gets to speed, its mostly fine, but I can still detect a slight degradation.
Ignition? fuel? Compression? I thought so.
I spent an hour last night doing the following:
The spark plugs are new, but I changed them anyway. I disconnected the rev limiter. I checked for spark... nice blue arc. wires are in great shape. I put dry gas in the gas, and new gas in, since I suspected a bad tankful. I drained most of the "old" stuff out (nice and clean, no rust, brass fuel filter), and have rode it long enough to be sure the new gas has been cycled though.
I have a lot of spare, good parts lying around, so its nothing for me to switch components. I switched ignition modules, and coils, no change. I then checked the fuel pump flow, OK. My nephew, the mechanic, laid the fear of god in me about a blown engine, so I checked the compression ... fine.
All of the above was not necessarily done in that order, but it was done. My next step, if I can't think of anything else, is to check the Vacuum to see if the carburetors are operating correctly. I suspect maybe the carburetors, but I rebuilt them last year, and other than linkage, I cant think of why they would react that way. The next step would be the spark pulse pickups (I cant remember their official name, but they are mounted inside the engine, and can be checked by a 4-pin connector under the tank)
Other than that, I am baffled. Any suggestions would be appreciated.
Solution (Addressed to Everyone in the MagSab Group):
Thanks for all your help on my Magna sickness. The problem was clogged main jets on the LF & LR cylinders. I don't know why I go on with really exotic, off the wall explanations, when the obvious is staring me in the face. After all my diagnostics last Wednesday night, I started out on Saturday morning with a vengeance. First thinking it was the fuel pump, in some fashion, I shorted the relay and drove the bike. Same problem. I don't know why I get these things into my head. I guess I wanted to get all the easily accessible stuff out of the way before I wanted to admit to myself that I had a dirty carburetor. Anyway, no exotic, easy explanations left, I pulled off the float bowls from the carburetors, and sure enough, 2 of them were clogged. This explained everything. Remember my feeling that it wasn't getting enough gas, and that it was running on 2 or three cylinders at above and around 5000rpm? That's because at that speed, 1 1/2 carburetors were not getting fuel through the main jets. (one was fully clogged, the other was partially clogged). I originally reasoned my way out of the clogged carburetor explanation with the reasoning that: if the carburetors were clogged, the performance would suffer over the full rpm range, not just the high end. This reasoning was wrong, because I overlooked the fact that the main jets are the deepest in the fuel bowl, and they would tend to clog first.
They weren't clogged much, and it was just a little rust. This leads me to the I used a brass in-line filter, with a replaceable element. I will never do so again. The brass filter obviously let bigger particles through than a standard paper element. I replaced the brass filter with a clear paper one, and I will use the brass one as a course pre filter. (yes, two filters!)
I could have just cleaned the jets, but instead I took a few hours on Sunday and rebuilt the whole darned mess. I didn't have to, it turned out, everything else was fine and unclogged. But the carburetors haven't been rebuilt for about 15,000 miles (last year) and I said what the heck. All the gaskets, O-rings and air diaphragms were in great shape, so parts were necessary.
The carburetors came apart with little effort. When I had the carburetors off last, I of course replaced all those worthless phillips head screws with corrosion proof allen head screws. On the bowls, top plates, and especially on the air housing. Taking off the housing from the carburetors is no longer an experience in trying to fit an impact wrench in there. I also did this on the exhaust, vacuum inlets, and anywhere else that used 4mm, 5mm, or 6mm phillips screws.
The only difficulty was, as we all know, putting the carburetors back on the engine. The easy way to do this, I've found:
There is no easy way. Well, Maybe there is. See below.
After putting everything back, and test riding, I found the usual neck jerking, eyeball peeling acceleration.
I also found an auto store that has NGK spark plugs, in stock, DPR8EA-9 for $1.59 each! The best price I've had so far is $2.50 mail order, and most auto stores in my area do not carry them. Those who do charge over $2.50 each! No more!
At the Run-what-you brung, my best run was a poor 12.2@112mph. I attribute this to the jets starting to clog. Out of the 10 or so other bikes there, 8 of them were GSXR11000's, (10.8 or so quarter mile), one ZX11, who I raced, who blasted me with an 11.1. I took him off the line, and for about the first 1/8 mile until he whizzed by me. There was also a V65 Sabre, in alright condition, who did one run of 12.9 against me (12.2) before getting kicked off the track for not wearing a leather jacket. The first run he borrowed someone's. It was embarrassing for him, the ref made him turn around and drive/push off the track.
Now that the bike is back in shape,
another night of drag racing is in order.