Fuel Issue??? Need Help

Hello All,

First post, nice site wish I know about this site years ago.

I was wondering if anyone can help me out with a problem I’m having. When I’m riding in any gear ant a steady low RPM the engine feels sluggish. It’s more noticeable at anything below 3500 RPM. It’s more of a feeling, like if you quickly tapped on the rear brake while riding. The tach doesn’t drop or flutter but you can feel the bike’s not running smooth almost like the engine is trying to rev or surge.

It’s got a Factory jet kit installed, 130 mains and stock pilot jets.

Last year I had the carbs synchronized and checked before I stored it for the winter. This spring it wouldn’t idle if the choke wasn’t on. I pulled the carbs off and checked the floats and jets. Three of the slow jets were completely clogged (that solved the idle issue). I also checked the timing, valve clearance and chain, all are fine. I even got some Sea Foam and cleaned the intake.

I’m thinking it’s running lean in the lower RPMs and I need to turn the pilot screws out a half a turn…any thoughts?

Thanks,
Wayne

 

Were the carb boots soft & compliant or a real pain? If they leak air a lot of strange things can happen. Might want to check the clamps & be sure they are tight. Try sending a personal message to squirrelman requesting input. He is knowledge heavy on these gen 2 carbs. Ask what he sprays to check for leaks? The gasolines we buy now days can plug up your carbs if they sit thru a winter season. In the future you may want to use fuel stabilizer like sta-bil or drain your carbs. DO NOT TOUCH the pilot screws yet!

 

Carb boots make a huge difference. I just got brand new ones that will be installed this week. My old ones are hard as a rock and one of them has a big chunk out of it, so I can't adjust the carb much since there's a big o' leak. Should be able to tune the carbs and get them sync'd by this weekend.

 

I’m assuming the insulators (boots) are original. I got the bike 12 years ago and they are kind of hard, no dry rot but they are stiff. I ordered new ones. The clamps are no longer available, so don’t loose them, got new screws though.

Last fall I filled the tank with Sunoco 93 and Sta-Bil then took the bike for a long ride. I thought that would keep the jets clean, no luck. This year I’ll do the same thing but drain the bowls before I store it.

If the new carb insulators don’t solve the issue, I’ll need a carb sync tool when I stare playing with the pilot screws. Can anyone recommend a sync tool? I was looking at the Carbtune http://www.carbtune.com/ about $88

 

Leaking boots really mess with the idle and low end, would make that my first stab if original and go from there. It is the first step. I assume it ran fine at one point during your owning this bike?

 

Sorry...forgot....nice gen 2!

 

Here's what happens when the carb boots get old, they break. This is why I had a leak. Should have better performance and be able to adjust and sync the carb now.

 

If the carbs were synced before last winter, they should still be providing that when you pulled the carbs you removed them as a unit, and removed the float bowls & jets in the bowl. If you left the linkage and sync adjusting screws alone they should be fairly close. You left the pilots alone & I am guessing you left the choke valves alone. Messing with "mature boots is no fun", falls in the struggle category, don't want to come off, don't want to go on!

A month or so ago Lazy in Arizona was doing this very same thing. He used carb cleaner spray to test for leaks around and on the boots by looking for increased idle. Someone else said a spray mist of water would causes a decrease in idle speed. I used WD 40, & the idle increased immediately, but shortly thereafter a nasty ooze came from the weep hole in the bottom of the muffler!

The symptoms you describe were very similar to what mine was doing. Nothing made any sense. When I got them tightened up, it was amazing how good it ran. Take a look at the clamps. They only tighten so far.They are not like a hose clamp. The service manual shows a specific angle for each clamp. I guess its to be reachable with a screwdriver. also each boot is marked carb on one side, & this side mates to the carb

I suppose another possibility is the chokes. If you pull the tank you can see the choke valves move when you pull the choke lever. Be sure they are all alike. Anotherwords all closed at once, then all progressing to to full choke at the same time.

I can't get by the fact that it was synced before last winter & I assume running ok.

Regarding syncronization. This gets all 4 butterfly's opening at the same time. The honda service manual uses confusing language ( in my opinion) regarding this & the pilot adjustment. The sync requires a manometer like the carbtune you mentioned. The honda manual says to adjust the pilots you need a tachometer that can register a 50 rpm change. The only one I have found so far is snap-on & I do not do enough of this to warrant the price.

Somebody shake squirrelman tree! Chime in here please!

Regarding carbtune. I view that as the cadillac manometer, and the price has come down. Theres another I recently ran across. Aerostich/RiderWearHouse Motorcycle Jackets, Suits, Clothing, & Gear :: Aerostich/RiderWearHouse Motorcycle Jackets, Suits, Clothing, & Gear Looks very interesting. And last the one I actually bought and have not used yet. Carb Sync Mercury Tuner. I think this was known in a previous life as carbstix. Easy to find on ebay, as by searching goldwing carb sync,etc.or going to Saber Cycle Honda Gold Wing GL1000, GL1100 and GL1200 Parts & Accessories. I bought the 08-010 carb sync tuner W/ 5 & 6MM adapters-motorcycle. $36.00 + $10.00 ups ground. Yes fellow cyclists thats $46.00 total aprox.I am not affiliated with them & do not know them, but I like the look and quality of this device. Also came with the little inline baffles that keep the fluid from gyrating radically. Another brand is motionpro.

I would sure check the spark plugs. I have heard people say a really rusty tank can send particulite fine enough to get thru the fuel filter and cause problems but I have not experienced that ever. And your air cleaner looks ok?

The foregoing is my view to the best of my knowledge based on my 86vfr700f. I do not have the california emissions model. When all else fails consult the honda manual:
poor performance at low speeds and idle speeds:
1. check ignition timing & valve clearance. if correct go to 2.
2.check carburetor pilot screw adjustment. if incorrect see fuel system section. if correct go to 3.
3.check for leaking intake pipe. if leaking:1.deteiorated insulator o-ring
2.loose carburetor.
3.damaged insulator (what we call carb boot)
4. performance spark test: if weak or intermittent: 1.faulty, carbon or wet fouled.
2.faulty spark unit
3. faulty ignition coils
4.loose or disconnected ignition system wire.
5.faulty ignition switch.
6. faulty engine stop switch
7.faulty cam pulse generator
8.faulty pulse generator

 

Clarification:merc carb sync tool thru saber is cheaper thru ebay than direct to website.

 

Check your plugs. Sounds exactly like what happened to me last month on one of the project bikes. Turns out the side electrode somehow broke off and was causing something like what you described.

Unfortunately that cylinder is now 20psi lower than the rest...but it sure runs better now with a working plug! One more motor To tear down.

I wonder what happened to that electrode...

 

Dear McViffer: Sounds like the electrode piece had a love tussle with one of your valves resulting in a less efficient valve. Lets hope it was reduced to small pieces that were blown out the exhaust.Honda bible says cylinder compression on the 86vfr700/750 is 199 + or - 28psi. I think that checked at operating temp. I checked mine cold and got no where near that but all were similar. Maybe thats not enough variation to warrant a teardown?

 

The whole problem started this spring when I took the bike out of winter storage. The bike had no idle without using the choke. The pilot jets were clogged. When I cleaned them I left the carbs together, I just removed the bowls. The gaskets were crushed and I found a place that sells just the bowl gaskets for $6 each, Bowl Gaskets.

When I put the bike back together the idle problem was gone but I noticed the ¼ open throttle issue. I just sprayed some carb cleaner around each boot and no increase in RPM. I was wondering if I open the choke just a bit when the issue starts, if it goes away then I need to re-set the pilot screws. If it doesn’t it’s not a lean issue at ¼ open throttle. Anyone agree???

 

I tried the choke test and didn’t see/feel much of a difference. I gave in and turned out the pilot screws a half turn each. The RPMs rose from 1100 to about 1500 (as displayed by the bikes tach). I dropped the idle back down to 1100 and noticed an improvement when I rode it. It’s not completely gone but I’d say a 75% improvement. My question is why after cleaning out the pilot jets why do I need to re-adjust the pilot screws?

 

Double check to see if your fuel filter is clogged. This happened on my '86 many years ago.
After that happened I always carried a spare new one.
Also, you didn't mention if your bike is a "49 state" bike or not.

 

When the pilot jets got clogged I bought a new fuel filter and lines before and after the fuel pump. The tank was a Cobalt fiberglass with a 10 year old Eastwood liner. The liner is coming off the tank so I put the stock one back on. The bike has no California emissions on it.