Stumped. What's going on with these carbs? Videos included

[Mightymouse]

Haters gotta hate...for what I don't know.

Your problem is coil wires.

No. See latest posts.

Your problem is spark plug wires.

No. See latest posts.

Worthless.

You ever been into a set of carbs?


Have you even been inside a set of carbs?

Not "worthless" and your tone is pretentious. This forum is to help people and solve problems.

 

[DreamV4]

del

 

[DreamV4]

del

 

[dannymax]

I suspect it was carb #1 or #2 on the right side where that popping was coming from. Looking back at those videos I took of right hand side carb #1 and #2 they do look whiter than carbs #3 and #4 on the left hand side.

M/M, carbs are numbered thusly:

front
2..............4

1..............3

 

[dannymax]

Hey all, want to update about this mystery.

I finally brought this problem to a shop and talked to them about this lack of power. They disassembled the carbs and found one of them had a loose jet needle. They corrected it and now the bike runs great. Acceleration is smooth through all the gears and WOT.

Also, it seems the "popping" sound has gone away as well. Not sure if this was also a symptom of the loose needle.

The needle jet was not properly secured in the jet block...the "popping" sound was the loose needle jet rattling against the back of the slide or the loosened retaining screw.

 

[Parminio]

What confuses me is that both right side spark plugs look like they're running lean instead of only the spark plug in the lean carb. Hmmm.

This is where I run out of gas on knowledge. That is a bit odd. Tied to the same exhaust pipe I would think that "could" effect it but I would also think it would be pretty minimal.

I'm not sure how the water runs through the engine though. I would be interested in knowing that because if the water ran through the bad cylinder and then the other cylinder that would make sense: the overheating was passed on to the other cylinder through the water and overheated that plug as well.

That's as far as my thinking takes me.

 

[Mightymouse]

Hi, i’m a newby here, but had my Canadian VMAX 1999 Carbon for 7 years. I’ve had trouble with these carbs where at 4-5 k revs the engine backfires, stutters and gets worse as the engine temp increases by the half way mark. The below is brief but hope it helps you out.[...]

Thanks for the detailed teardown/rebuild Screwloose. Well done!

 

[Mightymouse]

del

Hey DreamV4, yeah, final post will be a succinct summary of the original symptoms, the fix, and why it worked.

 

[Screwloose]

Thanks for the detailed teardown/rebuild Screwloose. Well done!

Thanks allot. Was nearly committed after 4 weeks on these carbs. I like to think I help out at times though, and bikers keep their sanity a bit longer.

After some additional thought and scouring through the site, there are a couple of things extra I would do on these carbs during set-up the next time their out. People have already done these on the site but I cannot find them again.

1. Find the fuel pump pressure and calculate the height for a false tank thus simulating the pump pressure at bench build. .
2. I remember someone on the site posting about using a light source to set the intake flaps, cant find that either, but credit where it's due, I would use that method in the future as there would be no touching parts to get the intake butterflies spot on, thus miniscule adjustment at carb snyc.

 

[DreamV4]

attach clear hoses (NAPA sells them) to carbs to check fuel level. If engine starts w/o choke, it means, engine runs rich, pilot screws should be turned in.

 

[Fire-medic]

using a light source to set the intake flaps

An old way to set butterflies or throttle slides was to use drill bits. The factory tuning instructions would say what size drill bit to use, to get the proper airflow at idle. This worked on single cyl's or multiple cyl's. Another way for synching carbs was to use the same size drill bit in each slide opening, and to get them adjusted so they all moved simultaneously with a throttle turn. This has been mentioned before.

Loose parts inside a set of carbs is an occasional problem. I've seen it before multiple times on used bike purchases. When I see that, it makes me wonder what other 'fixes' I'll be seeing, and it prompts me to give a thorough inspection for proper torque values to the fasteners like the brake calipers, wheel axles, front end, swingarm, engine mount bolts, exhausts, carburetors, and more.

 

[Screwloose]

An old way to set butterflies or throttle slides was to use drill bits. The factory tuning instructions would say what size drill bit to use, to get the proper airflow at idle. This worked on single cyl's or multiple cyl's. Another way for synching carbs was to use the same size drill bit in each slide opening, and to get them adjusted so they all moved simultaneously with a throttle turn. This has been mentioned before.

Loose parts inside a set of carbs is an occasional problem. I've seen it before multiple times on used bike purchases. When I see that, it makes me wonder what other 'fixes' I'll be seeing, and it prompts me to give a thorough inspection for proper torque values to the fasteners like the brake calipers, wheel axles, front end, swingarm, engine mount bolts, exhausts, carburetors, and more.

I use a drill bit all the time for that purpose, but you can very lightly scratch the surfaces of the bores and butterflies when doing it that way, I’ve also hit small rags on the drilled pilot holes that sometimes stick out slightly in the bore, then had to make sure they are clear. But always been successful in getting an accurate result when setting up multiple carb units, with just a very small tweak at syncing. I like the light method mentioned and will give that one a try next time.

Strange you mentioning torquing, just last year I’ve started using torque wrenches on as many nuts/screws as possible, and see it as something that is needed to be done allot more. I have reasons for that but I’ll not drone on, its certainly agreed in my view that it’s a good idea to look further into using torque wrenches more.

 

[Fire-medic]

The drill bit method of synching old-style throttle slides, not CV's, where the throttle cable was connected to the throttle slide, is what I was referencing. For my CV carburetors, I have a Motion Pro set of 'sticks' and a very-old set of bourdon tube gauges which still work well. I also have a set of NIB gauges, but haven't had reason to use 'em yet. I got them with a 'project bike' VMax, along with a lot of NOS parts.

 

[Screwloose]

The drill bit method of synching old-style throttle slides, not CV's, where the throttle cable was connected to the throttle slide, is what I was referencing. For my CV carburetors, I have a Motion Pro set of 'sticks' and a very-old set of bourdon tube gauges which still work well. I also have a set of NIB gauges, but haven't had reason to use 'em yet. I got them with a 'project bike' VMax, along with a lot of NOS parts.

I love the old stuff and have some great goodies myself from many years ago, such as my socket set when I was nine years old. In many cases the digital age has not surpassed the old analogue tooling, it just looks nicer, and reads easier for some people, but I love using the old stuff. I liked the old bike in the crate, you must have some amount of gear around!

As I'm going to be pulling the carbs out again I was wanting to use my false tank at a height to produce the correct fuel pressure on the bench float height set-up. So done a wee bit of calculating this lunchtime, and if anyone is interested the full results are attached. Some information such as fuel pump pressure comes way back 2020 from MaxMidnight and approximations to height results from 02GF74. There are some approximations to consider but I'll not go into that unless anyone wants them, as far as I can see M_M and 02GF74 are both correct considering M_M's original pump pressure range.

Height of false tank for G1 is between 2.28 & 2.83 meters, and that means it is do-able. Hopefully someone else can use this info also.

 

[Fire-medic]

Are you saying that you need to hang a tank at a height of nearly nine feet to get the same head-pressure as a Gen. 1 fuel pump?

I assume most uses for an auxiliary fuel tank is to replace the in-frame tank for purposes of getting a bike running? It's not like you're going to be running the throttle WFO. I've used an auxiliary tank at a height of ~ five feet and had no trouble supplying sufficient volume to the carbs. One exception was where I found the in-tank screen from a NOS Briggs and Stratton fuel tank had been partially-blocked by debris. That taught me the importance of checking everything in a temporary fuel delivery system.

 

[Screwloose]

Are you saying that you need to hang a tank at a height of nearly nine feet to get the same head-pressure as a Gen. 1 fuel pump?

Yes, there are many variables to consider, its a static equation, but there are assumptions such as gravity that changes over each short distance on the planet, temp, and product. For instance the temp of the medium under question changes density, as does sea level.
If its dynamic equation you need (flow) to take into account, bends, length, and pitting factors are more relevant for the equations. These equations are great as it explains air and fluid flows through systems such as motorcycles.

To add I get very excited over engineering equations, just remember Scotty on the Starship Enterprise.

Please remember static and dynamic are completely different items in fluid/air flows.