Critical Mass Yet Again - ‘90 Gen1

[desert_max]

So I got the last of the bits for these carburetors in today courtesy of one Sean Morley. And I’d like to take this opportunity to go on record and provide another testimonial to the service this guy does for the Vmax community. Yes, I bought a couple of inexpensive odds and ends from him this time, but needed a couple of other bits that he included for no charge. From his “scrap pile”. He could’ve charged me for them, but didn’t. Good old fashion business practices. You don’t find that anymore.

I’m running out of excuses to get this thing fired up. Got to get the carbs back on and the plugs are pretty badly fouled. I have two new ones, but need a couple more. Stay tuned.

The plumbing on these carbs was pretty bad, including a crudely fashioned inlet elbow.

Before:


After:

 

[one2dmax]

Awesome. Glad the casting was in good enough shape to work with the replacement fitting.

 

[desert_max]

Me too. Believe me.

 

[Denci]

So I got the last of the bits for these carburetors in today courtesy of one Sean Morley. And I’d like to take this opportunity to go on record and provide another testimonial to the service this guy does for the Vmax community. Yes, I bought a couple of inexpensive odds and ends from him this time, but needed a couple of other bits that he included for no charge. From his “scrap pile”. He could’ve charged me for them, but didn’t. Good old fashion business practices. You don’t find that anymore.

I’m running out of excuses to get this thing fired up. Got to get the carbs back on and the plugs are pretty badly fouled. I have two new ones, but need a couple more. Stay tuned.

The plumbing on these carbs was pretty bad, including a crudely fashioned inlet elbow.

Before:
View attachment 76099View attachment 76100

After:

View attachment 76101View attachment 76102

Good luck on the rest of the repairs! I agree with you 100% Sean Morley is a true Diamond in a glass world!

 

[desert_max]

OK guys, I think I’m in trouble. Back on page one of this thread, I mentioned that I picked this bike up that had been sitting for eight (8) years. However, with a new battery it started up, ran and revved… although it was running rather poorly. It was also pouring gas out of the vent tubes of at least two carburetors. Scary.

I figured I had a fairly routine carburetor clean up on my hands. Sure enough, the usual gunk in the bowls and clogged pilot jets were in evidence. Passages were cleaned and I threw it back together with all of the hardware it came with except one pilot jet that was replaced.

Gas is still pouring from at least two vent tubes!

Dang. I pulled the carb rack back off and open the bowls, replaced the float needle’s with some new aftermarket ones from the cheap kits I had on hand. They look identical to the needles that came out of it. They are still leaking. The seats are scrupulously clean.

What the heck is going on here? It is almost as though the needles neck is bottoming out before the tip fully closes off the orifice in the seat. Does that mean I have two sets of needles that are the incorrect length? I don’t know what else it could be.

Could someone take a quick look and measure the length of a known good needle for a Vmax carburetor? Again, I have no idea what else could be going on here. I am secure enough in my masculinity ask for a little assistance. Somebody please throw me a bone.

 

[Radioguylogs]

I'd be thinking if it might be sticky floats.

I've had the float shape out of round so it would stick on the float pin instead of rotating freely.

No gaskets hanging out or anything that would interfere with movement?

 

[user 16790]

could the float heights be out

 

[Fire-medic]

I measured two, one from a K&L kit, 15.34mm and one taken from a carb I tore-down, 15.37mm. I doubt the difference of 3/100mm is significant, as-long as you set the floats correctly.

Yours appear a bit-shorter than that, maybe 19/32. That's ~15.1mm.

Sean recommends a bench set, and then a wet-set, if needed, to the service manual measurement (15-17mm).

I usually use the round O casting as my bench-set. That's the left carb.

Are your springs in the needle valves freely-moving? They can become gummed-up, and sticky, where they will not work.

 

[desert_max]

Thanks guys, butI am running a fuel line from an IV bottle on the bench with the chambers open and the floats removed. The needles will not stop fluid from entering. That's why I was thinking they're the wrong size.

And 15.7mm is longer than what I have! Right? And if so, my hunch is correct. FM, please refer to the photo above and confirm based on your measurements.

The critical measurement is shoulder to tip. The needle hits a hard stop at the 3.5" point on the tape above.

 

[Screwloose]

Dang. I pulled the carb rack back off and open the bowls, replaced the float needle’s with some new aftermarket ones from the cheap kits I had on hand. They look identical to the needles that came out of it. They are still leaking. The seats are scrupulously clean.

I used aftermarket needles, and regretted it.

Comparing the old needles sizes and dimensions against the new aftermarket needles down to 0.01 mm, they were bang on size, diameter & angles were all correct. I re-newed the seats also and they were bang on size, but the strength of the springs inside the new needles were all different (and different from the originals) and threw my float height settings out by as much as 6mm when the engine was warm. Had the carbs out numerous times and the springs in the needles would not settle down. The aftermarket needles are junk and although the bike runs, it is not as good as it should be. Have you tried measuring the fuel height at temperature using the clear tubes (I'm absolutely sure you are aware of that but just mentioning anyway), as this is what gave me the clue on what was happening. The 28.5mm setting is great and is very close in every carb for first start up n(if you have Yam original parts), but when the engine is warm the aftermarket needles are way out due to the spring tension. Yes I did spew petrol out a few times trying to get the settings to settle down, even ran out of adjustment for the float heights, and still the spring tensions moved.

Next time (very soon) it's Yamaha parts only for me.

Hope that helps.

 

[Fire-medic]

Thanks guys, butI am running a fuel line from an IV bottle on the bench with the chambers open and the floats removed. The needles will not stop fluid from entering. That's why I was thinking they're the wrong size.

And 15.7mm is longer than what I have! Right? And if so, my hunch is correct. FM, please refer to the photo above and confirm based on your measurements.

The critical measurement is shoulder to tip. The needle hits a hard stop at the 3.5" point on the tape above.

I can see it going to 9/16" but the fluted body of the needle valve, including the viton rubber tip, is > 1/2"

Where did you come-up with 15.7mm? My measurements with rounding are 15.3 or 15.4mm.

Screwloose, I'm sure that you had issues with your aftermarket kit, because that's what you said. I will say that "all aftermarket kits are not the same." The K&L kits are made in Japan and Korea, and they are an OEM supplier for Honda, Yamaha, and Harley-Davidson. I've used their stuff for 40+ years, and I've had good results. K&L SUPPLY COMPANY - CARB & FUEL PRODUCTS

 

[Screwloose]

I used aftermarket needles, and regretted it.

Comparing the old needles sizes and dimensions against the new aftermarket needles down to 0.01 mm, they were bang on size, diameter & angles were all correct. I re-newed the seats also and they were bang on size, but the strength of the springs inside the new needles were all different (and different from the originals) and threw my float height settings out by as much as 6mm when the engine was warm. Had the carbs out numerous times and the springs in the needles would not settle down. The aftermarket needles are junk and although the bike runs, it is not as good as it should be. Have you tried measuring the fuel height at temperature using the clear tubes (I'm absolutely sure you are aware of that but just mentioning anyway), as this is what gave me the clue on what was happening. The 28.5mm setting is great and is very close in every carb for first start up n(if you have Yam original parts), but when the engine is warm the aftermarket needles are way out due to the spring tension. Yes I did spew petrol out a few times trying to get the settings to settle down, even ran out of adjustment for the float heights, and still the spring tensions moved.

Next time (very soon) it's Yamaha parts only for me.

Hope that helps.

I should have added that I also believe the viton rubber seals are crap material and expanding and contracting massively when wet/dry hot/cold. My experience of having an angle (tip) determining the length position of a shaft (needle), is that if the angle moves at all, or is very slightly out it throws the length of the shaft out by far. I'm saying that because the positioning of the new seats I used were slightly out in angle, but threw the tip locating seat length out by far, and I used Loctite shaft retainer to hold the seats in the correct positions. I really mean I was using a depth micrometer and micrometer to hold the seats in position while bonding just because the locating angles on the seats were out very slightly.

I had these carbs out a number of times during most of last summer, and came to the conclusions above over many weeks, many sore heads, and sleepless nights.

Hope it goes well.

 

[Screwloose]

I can see it going to 9/16" but the fluted body of the needle valve, including the viton rubber tip, is > 1/2"

Where did you come-up with 15.7mm? My measurements with rounding are 15.3 or 15.4mm.

Screwloose, I'm sure that you had issues with your aftermarket kit, because that's what you said. I will say that "all aftermarket kits are not the same." The K&L kits are made in Japan and Korea, and they are an OEM supplier for Honda, Yamaha, and Harley-Davidson. I've used their stuff for 40+ years, and I've had good results. K&L SUPPLY COMPANY - CARB & FUEL PRODUCTS

Just had a look for K&L as I'm absolutely going to change out the aftermarket parts, and if you have been using them for 40 years+ that's good enough for me. It appears though this is a US company with nothing here in the UK. There are some bits on Ebay but I avoid that route. Rumaged around in the workshop and it was Tourmax I used, very poor stuff at high UK prices.

I do not think I done anything wrong building my carbs up. I.E. I used verniers, surface tables, micrometers, even took into consideration surface tension height of fluid in the clear pipes as below LoL. When doing final adjustments to the float heights after running at temp I found a way of getting them accurately adjusted using a depth micrometer as shown below also.

All this mad extensive thought and precision went into these carbs, they still ran like s&*t on the bike. I really mean it was taking me that long to do this job that the seasons were changing.

I just noticed above that D_Max's needle wires that catch on the float tab are all the way around. This is the way I got my new ones, but the old ones looked original and only had 1 leg. When I tried to use the 2 legs the corner of 1 leg would very slightly catch on the edge of the tab (lifting the needle just a couple of thou). So I cut 1 leg off to be the same as the original. I do not think this would be the problem in this case, just an observation. Infact everything I've said above are observations, it sounds like you guys have stripped these quite a number of times. I'm just a very stubborn persevering theorist when it comes to carbs.

I'd better get off the internet and do some work, just hope anything I've said leads to something positive for you guys.

 

[02GF74]

Stupid question but are the valve seat free of debris?

Does fuel stop flowing past the needle valve when you hold the needle gently in place with a finger?

 

[Fire-medic]

I agree with Screwloose about poor-quality or aged, out-of-spec rubber tips causing problems with the seal in the needle seat. Having been coming of-age when carburetors were what you had to work-with, mention of swollen rubbers on the needle valve was always made in the rebuild kit directions I threw-into every Ford, GM, or Mopar carburetor parts kit I installed. I've never been a mechanic, it's just been my own rolling stock. Then there are things like gas-powered tools, like chain saws, lawnmowers, leaf blowers, pressure washers, generators, etc.

Screwloose is using some precise equipment there, much more-so than what I usually use to set mine. I believe the wet-check is the best way to confirm things if you're having issues with a problem carb, as he is doing.

 

[Screwloose]

I agree with Screwloose about poor-quality or aged, out-of-spec rubber tips causing problems with the seal in the needle seat. Having been coming of-age when carburetors were what you had to work-with, mention of swollen rubbers on the needle valve was always made in the rebuild kit directions I threw-into every Ford, GM, or Mopar carburetor parts kit I installed. I've never been a mechanic, it's just been my own rolling stock. Then there are things like gas-powered tools, like chain saws, lawnmowers, leaf blowers, pressure washers, generators, etc.

Screwloose is using some precise equipment there, much more-so than what I usually use to set mine. I believe the wet-check is the best way to confirm things if you're having issues with a problem carb, as he is doing.

F_M thanks for that as it gives me confidence to change out the needles and seats again. I've fiddled around with many carbs on cars and bikes but had no idea about swollen rubbers on rebuild kits, that's good news. I starting suspecting this swelling as I was reading every word you guys were putting on the site last summer, and I think it was you who said about swollen rubber on needle valves, it stuck in my head as a possible solution, and I'm 90% sure it has got to do with that. Yes; the wet check showed up allot of height differences of the floats (about 2mm in any direction), the initial 28.5mm size was very accurate for round 1, but definitely wet for round 2 there was movement as above. Also the engine temp twisted these values again for round 3.

As an aside; during my work in the oil game, there were many scenarios using viton rubber seals, and for sure there is a massive difference in quality for different prices of rubber seals. It appears the aftermarket needles I bought are poor quality. I would buy a set from your supplier Sean if he was willing to post to UK, that way I would know the quality I'm getting. I'll ask him!

 

[desert_max]

Wow: you guys are really kicking this one around and I appreciate it.

FM, yes I mis-read your number by a few tenths of a millimeter, but anything over 15 mm, if measured from the tip to the shoulder, is still longer than what I have above.

Also yes, since this carb rack is on the bench, I can hold the needle in the seat with my finger gas still pours through. Both when it first seats and with the button pressed down. They leak like a sieve.

The part that mystifies me, is that the two sets of needles I have - the ones that came with the bike that leaked originally - and the new ones that I had in those cheap kits both leaked. Granted, they both look the same, but I think that would rule aged rubber out. The photo above is an old one and one of the new ones.

The seats are scrupulously clean. You could eat caviar out of them.

Anyway, new needle valves are in my immediate future. Dang it. Now I play another delayed waiting game for parts to arrive.

 

[Screwloose]

Thanks guys, butI am running a fuel line from an IV bottle on the bench with the chambers open and the floats removed. The needles will not stop fluid from entering. That's why I was thinking they're the wrong size.

And 15.7mm is longer than what I have! Right? And if so, my hunch is correct. FM, please refer to the photo above and confirm based on your measurements.

The critical measurement is shoulder to tip. The needle hits a hard stop at the 3.5" point on the tape above.

D_M I've still got my old needles, and I think these were the originals. 14.5mm & 15.4mm (+0.1mm)

Notice 1off leg for the float tab, 2off tabs jammed on the new needles, so I cut one leg off..

 

[Fire-medic]

D_M I've still got my old needles, and I think these were the originals. 14.5mm & 15.4mm (+0.1mm)

Notice 1off leg for the float tab, 2off tabs jammed on the new needles, so I cut one leg off..



View attachment 76156

View attachment 76157

Yes, interpolation for measurement is 1/10 of the smallest graduation of the instrument, in this case, a vernier caliper. Your interpolative estimates seem reasonable and accurate. I see you have done a 'compressed-spring' and a 'relaxed-spring' measurement, showing that the travel is about 1mm, which also looks to be a reasonable length of travel for the needle valve pin.

Yes to crappy material in a viton seal causing issues.

One thing mentioned, about the wire stay for securing the needle valve on the float tab: in my experience, the OEM style is a full loop, and not a one-sided cantilever arm. Personally, I see no real difference in either type, assuming that the wire does-not interfere with operation of either the float or the needle valve. I've done replacements a couple of ways:

Use the one-sided, cantilever wire clip

Switch the wire loop from the OEM needle valve to the replacement aftermarket needle valve (which has a one-sided, cantilever wire clip)

I have never found a circumstance where the aftermarket K&L kits I use, interfered with the float movement or the apparent full-extension of the needle valve pin of the aftermarket piece. Neither have I encountered a difference in spring tension significant-enough that I could say that it exists, between and among needle valves. The only exception to that would be when a needle valve spring pin was gummed-stuck, not-moving, and then a shot of carburetor cleaner would free-it up, and the needle valve spring would display tension comparable to others in the carburetors. That doesn't mean that an indifferently-spec'ed/manufactured poor-quality needle valve cannot-have a flaw causing interference with proper float operation. That may-be one of the issues, and coupled with a poor viton material, that could be two-strikes (baseball-talk, U.K. guys, "three-strikes, you're out") against being able to achieve effective sealing and function of the aftermarket piece.

I think someone may have mentioned a defective carburetor float. Since these are solid, they don't tend to develop problems like the old-fashioned soldered-brass floats which were once-used in engines' fuel-delivery systems. Those could develop pinholes or wear-through, and become 'fuel-waterlogged' so that they would fail to properly display the buoyancy the float needed to operate properly. However, consider that some prior owner could have used lacquer thinner poured into the gas line after the fuel pump, to try and do a 'chemical liquid re-build' to clean-out the float bowl, the jets, and the needle valve and its seat, and that the lacquer thinner or whatever-other solvent used, caused a deterioration of the solid OEM float.

Plenty of ways that things can go-wrong in a carburetor. You need to tackle them one-by-one, as they are identified, and solve them. Careful inspection, use of OEM or equivalent replacement parts, reassembly according to factory specifications, and checking for subsequent proper operation are how-to solve these 'gumption traps' (thank-you Robert Prsig, Zen and the Art of Motorcycle Maintenance).

Sean Morley, dannymax, and CaptainKyle are three of the pros here who do this for a living, I'd defer to any of them for an opinion on this subject beyond my hobbyist ramblings.

One way to avoid issues is to go with OEM, rarely will you ever encounter a bum part from Yamaha. In fact, my first new bike was a Yamaha 360 Enduro, 49 years ago, and I cannot-say that I recall since that time, having received a bad part over the dealer's parts counter. I've owned more Yamahas than anything-else: standards, cruisers, and sportbikes included, and I've owned bikes from the Japanese Big Four.

 

[desert_max]

I think I see the problem here gents!

That miserable double hoop wire that Screwloose is talking about. Notice how it affixes to the top of the float needle on my needles. Take a look at the at the photo he uploaded with the calipers. See how the activating wire doesn’t interfere with the travel of the needle? I believe that stupid wire is preventing the needles I have from fully seating. K&L needles don’t have this problem - I’m looking at them now.

They’re pretty darn expensive, but I’m springing for a set right now. I’m tired of messing with this thing.

Surely I am not the only one who has ever encountered this…?