carb woes

[tinman22]

I've been working on the carbs of the bandaid motor for several days and i actually think i am getting dumber by the minute.

I have a bike that starts hard but idles like a watch and the second you touch the throttle it dies. I have had them on and off three lunches, two dinners, one 30 pack, and i'm considering taking up smoking.

stock paj 1 and 2, mic 150 mains, stage 7 springs and needles on the 2nd from the dull end, air correctors, velocity stacks and big k&n filters. Floats set/checked properly seven pudding cups. Fresh fuel filter, spotless fuel tank, synced,synced and re-synced.

valves were just adjusted properly, cleaned up a wiring rats nest, new rectifier (late model stock).

Any idea what i missed? or is it just time to buy a GROM?

 

[desert_max]

Fuel delivery issue? Is the pump doing its job? Sounds like it's starving.

 

[Fire-medic]

AIr leak? Do you have the stock airbox to re-mount?

This is a used bike you got, have you cleaned and re-oiled the K&N's?

 

[tinman22]

fuel pump cycles and bowls fill up. it will run with the choke on but is still boggy and won't rev freely. I have had them off at least a dozen times. after they we're completly cleaned and reassembled it would start and die. since the rebuild I have done the shotgun, the peashooter and the hokey pokey and all blows thru nice and clean.

Before I "fixed" it i actually rode it to a friends house 1/2 mile shut it off and it was a hard start but it rode home. valves we're really tight so i adjusted them.

It is starving for gas, if i put the air box on i can spray gas from a windex bottle in and it actully runs pretty good just not very practical.

I thought air leak to but couldn't find one. also the rear cylinders 1/3 idle at about 400/500 degrees, the front two 2/4 would only get to 250 on 2 and 175 on 4. After cleaning rears are at 4-5 fronts are 350-4 with mixture screws at 2.5 on all 4.

ive swapped k&n pods (light oil) two big k&ns oiled both with and without stacks. Not sure how the stock box/filter would react with air restrictors.

Tomorrow is another day. I can have them off disassembled gone thru and back on in an hour..... so 10 more attempts....Damn even a blind squirrel gets a nut once in awhile.

 

[tinman22]

I'm going to put clear tubes on the float bowl drains tomorrow and watch the fuel level. If nothing else it will be neet to watch.

 

[totalcomfort]

I feel your pain, I just went thru this. I was a wiz with Holley carbs back in the day when I raced. I gave up and bit the bullet and sent them to Morley's. Wasn't cheap but worth every dime. I got them back and had 1 minor issue which he answered quickly via email. Bunch of little quirks with these carbs that takes some time and skill to master. Save the headache send them out.

 

[tinman22]

I hear ya. problem is this isn't my first time. I have successfully rebuilt these 7/8 times. I know its nothing compared to guys like sean but i should be closer than this.

what has got me is the exhaust temps that are so far off. I would really hate to send them off only to get them back and it runs the same. I think i will mount them backwards tomorrow and see what happens. It will eliminate a whole slew of possibilities in one shot.

 

[MaxMidnight]

Can we assume that the carbs are synchronised and that you have checked the integrity of the diaphragms?

Given the time you have put into this already I think my next move would be to get them ultrasonically cleaned to ensure all internal passageways are clean and free of cr*p.

Whilst there is the possibility that you may still have the issue at least you will know one thing that it isn't.

 

[Parminio]

AIr leak? Do you have the stock airbox to re-mount?

That sounds likely. Get the bike cranked and idling and take a can of carb cleaner with the straw on it and start spraying short burst around the rubber carb mounts top and bottom.

Also shoot some short burst around where the manifold seams are.

If you hear the idle change at all, you've got a leak.

Edit to add: How do your plugs look?

 

[Screwloose]

That sounds likely. Get the bike cranked and idling and take a can of carb cleaner with the straw on it and start spraying short burst around the rubber carb mounts top and bottom.

Also shoot some short burst around where the manifold seams are.

If you hear the idle change at all, you've got a leak.

Edit to add: How do your plugs look?

I had my carbs in and out several times a few months back. What I should have started to do was the above first, as Trigger was running smooth on tick-over but when the temperature came up it was rough at around 3k revs. The initial problem was as the temp comes up the rubbers top and bottom are softened, then if the rubbers are split anywhere they leak as you accelerate (my rubbers were split at the edges of the clamps and difficult to see). Rubbers perish if unused.
Drawing air then runs a lean engine and temperature at each exhaust outlet will vary by a large amount.
I also set them up with fuel level tubes showing where the lean/rich levels at mid temperature were, and persevered with the float heights.
It was all a real pain as I done several other tasks on the carbs. Trigger now runs, but is slightly lean, so it's carbs back out again later.
The reason I done all this myself is that I hate giving in to anything, enjoy being a knowledge seeker, and like to be personally close to my bikes, cars and vans. But if I had known the time effort would be so high I would have sent them away to get done. Although again I'm in Scotland and I cannot think of one outlet I would let touch Trigger. Maybe with this Brexit thing I could send them over to the guy everyone mentions on this site. My view is that do it yourself and gain knowledge and experience, but also use the advanced tools available if possible if it makes for a better job. I mean; would you saw a tree up with a fishbone to make a canoe, or submit to technology and buy a saw?

 

[tinman22]

yup all the diaphragms are good. Plugs are new but it's hard to say how they would look as a diagnostic tool. as they are always wet and black from the dying process. Manifold rubbers looked good but i will give them a closer look.

Im going to toledo today for oven parts for the powdercoater. They sell industrial supplies and things like sonic cleaners. I will pick one up. I think work needs it.

 

[Fire-medic]

If temperatures aren't higher at idle, then you have a plugged circuit where that low-temp cyl is malfunctioning. I'd start from the beginning, at removal/disassembly. I usually don't remove the enricheners for an ultrasonic cleaning, but I do open them, and after the bath, they get doused in the enricheners with wd-40 or CRC 5-56, and screwed back together. I bench check the float levels, make sure all passages are flowing air, same for the jets, and reassembly.

I think you need to check for vacuum leaks, the best way I know-of, is the way Parminio describes, which I've mentioned many times in other posts. It's quick, it's simple, it doesn't require $$$ equipment, and it works. I keep some carb donuts on-hand, and the VBoost to cyl head thin O-rings too.

While all those parts are daunting on an initial disassembly, after a few times of teardowns, and reassembly, it's easier, quicker, and effective. I can understand that sometimes it's beyond the scope of work an owner wants to attempt, and that's where the guys on-here who do it as a business are worth paying: dannymax, Sean Morley, and CaptainKyle.

Yes a poorly-operational bike is frustrating. If your diagnostic skills aren't giving you an effective diagnosis, it's better to use one of the professional guys to set things right, and get back on the road.

 

[tinman22]

I forgot today is national hangover day. guess i'm staying home.

 

[02GF74]

Also check the enrichment plungers go all the way in once you push the choke in when engine has warmed up.

 

[tinman22]

well I pulled them back off. I checked the rubber manifolds they weren't bad but I had another intake with nice ones so i took it off and swapped it. I also found that the v-boost butterflys had been molested and were out of sync on the old one. While the carbs were off I did another comp. check all were at 125 +/- low I know but at least even. replaced the bowl drain tubes for a foot of clear hose each, reset the mixture screws to 2.5 out each. pulled the diaphragm covers and checked all the jetting again 90/170/150 needles on the second clip from the blunt end and all the air correctors still there then put them back on.

checked the k&n's and plugged the fittings for the stage 7 vent hose. zip tied the bowl hoses loosly to the frame and cracked the bowl drain screws.

three key turns to fill the bowls. started on choke and warmed up choke off.

idle at 1000+/- and synced them to #1@22in. #2@23 #3@23in. #4@22in.

idles fine. blipping the throttle shows a slight stumble. raising the r.pm. slowley reveals a more defined stumble. holding it at 2000 r.p.m. it will stumble, sputter and then die.

cylinders 1/3 are still hotter than 2/4 but not as bad 50-75 degree difference.

fuel level is interesting. Floats were set at 1.12" after filling the bowls the fuel levels in the clear lines were all even +/- 2mm in the line.

However while running the levels swing wildly even at idle. Sometimes being 10 or 15mm different. also when I shut it off the pump doesn't fill them up on the next key turn. To get the pump to fill them you need to drain them then cycle the key three times to get them full.

I'm going to swap the pump for a new one from another bike tomorrow and see if the fuel level is less erratic.

Better but still not right. maybe tomorrow. plus I can't send them off to get done until I have spent at least the cost of the professional rebuild getting nothing done.

 

[Screwloose]

Did you know the fuel levels change when the engine is at temperature. I put 2 household fans at the engine to try and hold mid temp at the gauge. Setting the float heights cold or on the bench just gives a fair starting point.
I also use the fans for temperature stability when synchronising the carbs, but initially set the butterflies using a drill bit shank, it gives a closeness without synchronisation allowing a tick-over when the carbs are just installed.
My fuel levels bounce on #4 especially and gets worse as the engine creeps by the mid temp mark. So i hold the engine at mid temp and take all my readings from there, strip and re-do the float heights again. Also i use a depth micrometer to take the float heights at a certain point and it lets u adjust them within about 1/4 mm. if you watch your tubes with fuel in them observe the heights at temp’s, also you need to systematically lift the tubes up and down to keep air out of them,
there may be more reasons for the fuel level bounce, i’m no expert on these, but i find it relates to temp.
Hope that helps. I have some photos if that also helps.

 

[VMAXXIMUM]

"Floats were set at 1.12" after filling the bowls the fuel levels in the clear lines were all even +/- 2mm in the line. "
Unless I'm missing something that would be 28.44mm. Spec is 15 to 17 mm or .59 to .66"

 

[tinman22]

right you are. factory spec is 16+/- 1 mm. Below the line on the side of the carb.

 

[tinman22]

but i did it this way

 

[tinman22]

which also translates to 16mm from the top of the float to the metering block?