belt snapping issue found ( 99.9% sure ), 2 reasons.

[br4inl3ss]

Jul 21, 2023 8:17:09 GMT -5 GrumpyUnk said:

That diaphragm is cooked. Originally it had a 'tab' that stuck out from the outer edge and fit into the recess shown at about 7-8 o'clock. And it must sit in the groove around the outer diameter. If not, it won't seal and won't function.
The first 2 pics(CVK) look about right. The float should be about 90 to the face of the air inlet. Parallel to the floor when inverted into normal position.
The 3rd carb pic is your italian.. I think, and it appears to me to be set too low, so the fuel level would be lower in the bowl than I would have set it at.

It seems that many lose the washer and O-ring that are buried down the idle mixture port. The screw pushes on a spring, the spring on the washer and the washer on the O-ring. With parts missing, on the floor, or fallen out and never even seen, the mixture screw does not work properly. It will allow air past the threads. Threads do not seal. They will leak liquid or gas. Unmetered air can mess up the idle stability.
Are you sure the O-ring and flat washer are installed?
I did not watch the vids except the last.
tom

Thanks Tom.



I don't get what you are talking about with the tab on the diaphragm... It's there, properly installed, and all of the diaphragm seems fine. All the carb I had had the same issue brand new including the keihin.



All my carbs but the stock junk have all their parts nothing is missing. I'll recheck to be 100000% sure but they were complete.



yes 3rd pic is the dellorto phbg. i put it level as they all said it should be, but then after i tried to put it like that. no change.

they all say the line on the float should be level with the bowl surface. it wasnt. it was slightly inclined, exactly like in the picture. so not sure who is right...they also all say they all come perfeclty setup. false. mine was inclined jsut like on the photo.





what is weird is that there is absolutly nothing that can be done to make those carb works properly, and whatever i do doesnt change anything.

with the dellorto, idle si still way too rich, hard to tune, and too lean at WOT, but damn, everything i try actually make changes. richer/leaner with and without both at idle and WOT.



weird.



if diaphragms are all cooked, BRAND NEW never opened, even the overprice keihin i had, then i understand why so many people hate those carb... even a yamaha stealership hate them.



for the float level, to me it seems fine on the cvk carb. as you said. did it by eye since the guide on here doesnt make any sense. using the measure they give make it overly inclined, far from 90. pretty sure it depends on the carb because i have yet to find a guide here that isnt right.



just re-tested the dellorto phbh today, since Motomode ( the shop that install alot of thsoe carb on 4t scooter and motorcycle because people hate cvk ) said the small scrw on phbg are AIR screw. so to lean out the mixture they msut be turned counter clockwise. noce sure he's right... i turned it out so much i completly removed it. engine got rpm's ( to about 5k ) but still way too rich. put it back in held vby finger not screwed in, rpm lower a bit. only change is that the engine take acceleration way better. but the same way as completly screwed in. so not sure who is right again. is it a AIR screw or a FUEL screw... always tought it was FUEL screw ( so clockwise = richer )... but its so rich, i cannot tell which way is what exactly.

i was able to get a decent ratio when i turned the wideband on, but would barely idle and then stall constantly ( 1300-15-- rpm ).



they made me spend money on a dellorto, ill keep and use it. but pretty sure my problem is NOT carburetor related even tho the pgbh work a billion time better. doesnt work good at all, but billion time better than all of my cvk.



timing is correct ( not even a tooth off ), valve gap doesnt change anything about this issue ( right now at .004/.005 ). and i did check again for vacuum leak. cannot find any.



only place i didnt check is where the intake meet with the head, thats because the damn engine shroud is on the way. but iirc i already tested that when i didnt had it in.



as you see i test everything people say. nothing fix the issue. and the whole damn engine have been rebuilt because of that stupid issue.

[GrumpyUnk]

Not knowing the age of your bike, I would note that the O-ring style gasket on the cylinder head side of the intake elbow can get flattened over time, and fail to seal adequately. That would hold true no matter how many carburetors you install.... and you have quite an array...
It is easy to remove on most 4Ts, with just two nuts. You can even leave the carb attached if you are nimble.
Look at the rubber and see if it protrudes above the surface of the elbow. It should do so a tiny bit.
I have used RTV to insure a seal on some. I take a dab and smear it across the whole surface. I think it helps seal where the O-ring is perhaps questionable. I do NOT put a blob on there, or do a 'ring' around the port. It is just a smear to add a tiny fraction of malleable material that will conform and improve the seal. I have also done that on rocker arm/cam cover gaskets when they were old and somewhat hardened and I didn't have a replacement handey. Again, a wipe that will conform to the O-ring and to the top of the cylinder head. Seems to work, but there may not be much oil trying to escape from the cam cover.
tom

[dumkid]

You've probably checked this, but is your cam timed correctly? If the intake valve doesn't close at the right time it can push air back through the carb resulting in more fuel being drawn into the intake. Just a educated guess

[br4inl3ss]

thanks.

@dumkit
yes i checked. about 3 time in the last week, once again.
il be going back wo valve gap of .002/.003 since .003/.004 is noisy and doesnt fix anything.

@grumpyunk
yup i verified that.
i even push up to 110 psi ( hard to keep adapter in place ) thru the intake ( in palce of the carb ) and we can head absolutly no leak. also removed the shroud, and sprayed soapy water ,cant find any bubble going out from anywhere again, not even there. put back one carb , still no shroud, started it, held it around 6k rpm on stand and tried all the possible thing i could think of. includign propane, acetylene, wd40, carb cleaner, brake cleaner, gas, octane bosoter... EVERYTHING. its sealed better than a damn submarine.

now that i have jets for the phbg, i get it idling fine with a 30 pilot jet ( smallest possible anyway ). i know i cant use 36 its too big, but i may try with 32 soon.

thing is... its way too lean on acceleration. but in a weird manner.
ill try to explain but i got a video showing it.
when its cold, no way to give any throttle it stall immediatly. thats fine. but when hot, i can give QUICK throttle ( any position be it 1% or 100% ) it will rev up fine up to 6k rpm ( main jet of 98 still too small, ordering more soon ). but after 3-4 quick rev, it wont rev anymore will just stall. same happen with and without airbox. didnt feel any difference either but whatever. maybe im just too focused on trying to fix this shit.
when it swall, i can start it back and restart the process over again ti will act exactly the same: 2-3 quick throttle works, then after it just lean out progressively with each action on throttle.

ok fuck my bad english, here is a better way to explain





one guy told me its because a 2t carb will NEVER work on any 4 stroke ever. but we have proof around that it does work and pretty good.

ive seen 2 4 stroke with phbg here. duno the size and setup but ive seen them at the school parking lot and i saw them going out. they work better than mine ever did with cvk carbs
there is also rolling wrench video of his PWK kit on 150cc gy6. it may not be perfect, but thats still better than mine ever worked. with whatever carb i had even stock one.
and there is the french guy channel, Simon, that prvoe it work.
see it yourself, we can see he still runs the phbg 19mm he installed on rpevious video and there is absolutly NO throttle problem at all.


i dont think main jet too small cause this issue ? well with my cvk this doesnt happen wven with 50 jet when 90 is needed. but maybe phbg are different ?

the MotoMode guy said the stock phbg 45 pilot jet is perfect and very rarely need to be changed. LOL. i need to run 30, and ive seen sone run 32 and 35... so maybe he was also wrong when he said i shouldnt have to change needle or slide ?

EDIT forgot to mention, idle is already rich ( 12:1 to 13.5:1 ).

[GrumpyUnk]

but after 3-4 quick rev, it wont rev anymore will just stall.

Either it is running out of fuel... flow can't keep up... or you are getting the engine too hot, and it is starting to bind the piston in the bore. Maybe.
Use a plastic soda bottle with a hole bored in the cap. Make the hole so fuel line that fits the carb inlet is tight and won't leak. Stuff fuel line into the hole and connect the other end to the carb fuel inlet port. Partially fill the bottle with fuel. Hold the soda bottle inverted and start the engine. Do the 3-4 quick revs and see if it will do more. If it does, you are lacking fuel... If not.. well lemme think a minute.
I suspect you are getting inadequate fuel flow. Why? Just because.
tom

Added... Watched/listened.

 Well, that was 9-10 throttle rips... not 3-4.  It sure sounded to me as if it was out of fuel.  IF it has an accelerator pump(some do, but mostly for bigger displacements) then it did not have time to recover and bleed fuel into the pump reservoir.
 The CVK accelerator pumps have a tiny orifice in the float bowl to fill a small reservoir that is used to feed the accelerator pump.  If you empty the reservoir by doing multiple twists of the throttle grip, the pump will not longer give a squirt of fuel for each twist.  It cannot, as it must wait for the reservoir to refill.  Same deal on the byvalve reservoir, but most don't care as it will get refilled before the engine cools enough to operate the byvalve... in most cases.
 One test would be to attach a hose to the float bowl 'winter drain' used whenever the bike is stored.  Feed the hose to a suitable container for fuel, and open the drain screw a few turns(as needed).  Fuel should flow from the float bowl.. and keep flowing as long as there is fuel in the tank.  This will check fuel lines, filter, petcock?, fuel tank outlet screen... If you do not get full flow 100% of the time you have(may) found your problem.  IF you have any fuel line that is old, note that it can deteriorate on the ID, and form clogging deteriorating line that breaks loose or hangs, impeding fuel flow while the line is looking good extermally.
tom

[br4inl3ss]

thanks.
ill try that, duno why i didnt think of that, its a known trick when bench testing engine ( v8 in my case ).
i know for a fact its not getting too hot thats for sure.

meanwhile, do you have any idea why a phbg 19 require a bigger main jet than a cvk 20 or 18.5 or even stock 17.5 ?
with my cvk it needs 90. with phbg the bigger i have right now is 98 and its way too small.
im ordering 110 115 120 and 125 tommorow. they are easily available and only 4$ CAD each ( dellortho ) or 3$ CAD each for MS24, they they keep a HUUUUUGE stock of them. think the local dealer order from this supplier only once every 2 week unless i pay 13$ more. with my limited budget, all i can hope is that they have an order planned soon lol.

[GrumpyUnk]

The vacuum diaphragm and slide move slower than you can with a cable op slide. The mix on old SU carbs was set by using a thumb button on the bottom to lift the slide ~1/4" or less. That lifted the slide from 'idle'. There would be a quick inrush of air into the manifold. If the SU jets were set properly(using a screw to adjust) the idle rpm would bump just a bit as you tickled the button. If too lean, it would stumble. Too rich and it would not have the 'bump' as the extra air was already accounted for?
Any way a mechanical slide needs SOMETHING to cover for the fact air accelerates faster than a liquid(density) and the fuel:air mix coming in off idle will go LEAN if you don't add some fuel to cover the lean condition until the fuel liquid can get moving inside the passages.
The bigger jet allows that quick off the idle mix to be rich enough to allow it to slide past the lean.
At least that's what I think it does. Also, remember, a 2T wants fuel 2x as much as a 4T. It will be vacuuming the intake manifold on each down stroke while the 4T is still fumbling around doing compression & firing... etc.
It must essentially flow 2X as much fuel... for each rpm. No?
tom

[br4inl3ss]

thanks.
i understand that. but how do they do ?
they actually do its not fake. just no one answer on videos and the 2 scooter ive seen with phbg i cannot get in touch with them. maybe if i keep going there and wait till they get out of the job but i dont have such time to waste. and its pretty far away. but if i knew mine would be different id had took pictore of them. one it flat black the other is stock orange color.

my idle is already rich to the max. needle position doesnt help.
i disabled accelerator pump on my stock cvk carb and tried, work fine without it.

[kosmos]

Aug 6, 2023 18:01:45 GMT -5 br4inl3ss said:

@grumpyunk
yup i verified that.
i even push up to 110 psi ( hard to keep adapter in place ) thru the intake ( in palce of the carb ) and we can head absolutly no leak.

you leak down test using 3-4 psi only because you can blow out your crankshaft seals.  are you sure you have your valves open or whatever it is you do during a leak down test on a 4-stroke, that you don't have some port blocked off and your not testing the crankcase or something?  
it sounds like in your video, an air leak.  or a lean carb setting.  you havent taken it apart and forgot an o-ring like behind an idle set screw or mix screw  or something?  
what about when you adjust your idle.  thats how i keep mine from cutting out is adjusting my mix screw until it doesn't cut out.  too rich can cause it to lag and too lean will cause it to cut like in your video it seems like.  
this is my opinion but, I think as long as your within 1 size of the right pilot jet that the mix screw will work within the right/tuned range.  like ive had my bike not cut out but been 1 size too large pilot jet before.  id have other problems tho instead with the bike higher up in the throttle.  and if i turned my screw too low/lean, it would cut out.  and the screw would be within the 1-1/4 - 3 turns.  that seems like a mixture screw that needs adjusted.  or a jet too far to the lean maybe rich side.  thats how I keep cutting out from happening on my bike is adjusting one of those things then the other.  using the mixture screw to fine tune it with.  

[br4inl3ss]

Aug 8, 2023 4:03:00 GMT -5 kosmos said:

Aug 6, 2023 18:01:45 GMT -5 br4inl3ss said:

@grumpyunk
yup i verified that.
i even push up to 110 psi ( hard to keep adapter in place ) thru the intake ( in palce of the carb ) and we can head absolutly no leak.

you leak down test using 3-4 psi only because you can blow out your crankshaft seals.  are you sure you have your valves open or whatever it is you do during a leak down test on a 4-stroke, that you don't have some port blocked off and your not testing the crankcase or something?  
it sounds like in your video, an air leak.  or a lean carb setting.  you havent taken it apart and forgot an o-ring like behind an idle set screw or mix screw  or something?  
what about when you adjust your idle.  thats how i keep mine from cutting out is adjusting my mix screw until it doesn't cut out.  too rich can cause it to lag and too lean will cause it to cut like in your video it seems like.  
this is my opinion but, I think as long as your within 1 size of the right pilot jet that the mix screw will work within the right/tuned range.  like ive had my bike not cut out but been 1 size too large pilot jet before.  id have other problems tho instead with the bike higher up in the throttle.  and if i turned my screw too low/lean, it would cut out.  and the screw would be within the 1-1/4 - 3 turns.  that seems like a mixture screw that needs adjusted.  or a jet too far to the lean maybe rich side.  thats how I keep cutting out from happening on my bike is adjusting one of those things then the other.  using the mixture screw to fine tune it with.  

thanks.
what crank seal ? its already done. yup, again. so i dont care what happen to it.
but today i just picked the naraku seals kit i ordered 6 weeks ago ( i even forgot about it. dealerchip game me a call that my item arrived... wait what ? i didnt order anything... so i didnt even ask what it was and i went there to see. ).
quality seals should make a difference instead of cheapo seals.

buy it wasnt a real elak down tst. a leak down test require 2 gauge.
i dont have any i just rely on air noise.
it was more like a simple unerliable leak tester.

and as i said like at least 15 time ( and verified 15 time lol ), no leak to be found. if there is one ( very possible ) then its hidden better then ben laden was because its impossible to find. not with the tools i have, at least.

this doesnt happen with my cvk carb. instead, they're TOO RICH on throttle. but slow or quick its the same. its related to throttle position.
i dont think its an air leak. but what do i know... i cant find any. doesnt mean there is none tho.


i was doing the test Tom suggested to verify fuel delivery, kickstarter broke so it was the end.
i ordered one on amazon and should get it tomorrow.
also i should get 4 phbg main jets ( 110 115 120 125 ) tomorrow at the same palce i got the seals. paid to get them tomorrow, else it would be on thier next order aka 3 weeks. 98 is way too small yet.


is there any other way i can try to find an air leak ? the old tricks used sicne years doesnt find any. weird, those tricks always worked perfectly. on my atv and car at least.

[kosmos]

build you a leak down tester. compression gauge, the hose it comes with screws right into the spark plug hole, bonus you have a compression tester too. 3 way npt pipe adapter. get a pressure gauge that doesnt go very high and fits the 3-way npt hole size or you can get adapters. want to be able to read 3-4psi. a bike shraeder valve that has npt pipe fitting, i had to get one of these online. and the right compression gauge kit has a clip on thing for the hose that you pull back and it goes into. on the tester kit you can unscrew its clip on thing and hook it up to your 3-way npt adapter. use pipe thread tape on all 3 connections. remove the valve core out of the compression hose, dont lose it its for a compression tester and a tire valve core won't work right. plug off your other holes in your motor, on 2 stroke thats for me, exhaust and intake. use an old intertube, cut out a block off. some paper gasket material behind it to make it level and something flat and hard to hold it down with. screw the compression hose into the spark plug hole, and make sure your motor is set up right, on a 2-stroke, make sure the piston is at bdc, not sure on a 4-stroke im sure someone can come along and answer.
pump it up to 3-4psi and check your connections and your block offs first for leaks with soapy water. then check if your losing air on your gauge. if you are, check around all the gasket sealing places and seals and find the bubbles.
if you don't have any leaks then it might just be carburetor tuning. i had a leak that wasn't being picked up, I think a vacuum tester would have found it but. it was kind of obvious it was having a problem and when i took it off, my bike tuned.

just make sure your tuning your carb right. put the best pilot jet that gives you the best idling. dont turn the idle adjustment screw too far in, if you have to it might be going onto the next circuit in the carb jet tuning. once you have the best idling pilot jet in. adjust mixture screw make sure its 1 1/4 to 3 turns out and no more or less. then rev the bike back quickly and see if it bogs or cuts out. if it does, adjust the mixture screw until it works right. Maybe try the next higher pilot jet or one lower and retry again if you cant get it to work. if not that then, if your using the phbg, make sure you have the right atomizer in there. there are different sizes but that shouldn't really matter too much on the initial rev back. if it cuts out like yours did on the video then that seems like airleak or pilot jet.

[GrumpyUnk]

Wander on over to YT. Make a smoke machine. Using a plumbing drain fitting and a few others, a length of wire, and a fiji lamp wick you can make a smoke generator for ~$30-ish.
Attach to the intake via any port, and pump with a bicycle tire pump. You don't need a lot of volume or pressure to push smoke out of any leaking spot.
here is one:

www.youtube.com/watch?v=crc6CJ_ni2w&pp=ygUQc21va2UgdGVzdGVyIGRpeQ%3D%3D

Do a search for 'smoke tester diy' to get some suggestions.
One starts at $10... but scrounging can make it less, ditto substitutes.
I built one, almost, but need to connnect terminals and fittings.
I am going to use motor oil as $5 for a little baby oil, scented mineral oil, is a bit much.
tom

[br4inl3ss]

i did have one i made when i had my modified truck. but i ran over it

ill make another one...

but i have more issue...
first, the main jet i got have the head smaller than the stock dellorto and my motoforce racing jets. it fit well, they're exactly the same everywhere, even head thickness. but smaller head.
duno if its normal, but whatever they fit well and i'm done waiting aprts for months.

kickstarter broke... ordered one on amazon, aka the ONLY available one without waiting it 2 months, and its not the good one. doesnt fit the measure they give on the description and images. well.

guess ill have to cut&weld that thing too...

so done with this nightmare. imagine if it was POSSIBLE to get something else............

EDIT:
put the 110 main jet in... its a BIT better ( happen less often and a bit softer ) but 110 is way too big.
just ordered 100 102 105 108. and another 30 $ spent...................

[br4inl3ss]

UPDATE:
tested fuel delivery, same shit happens. no difference at all.
fuel delivery is fine.
and it wasnt any better after more testing testing ( before testing fuel delivery ).
it just seemed better but wasnt.

waiting my main jets, but they are ofcourse not the cause of the problem.

thats so damn weird... with cvk's they're too rich so terrible quick throttle, and with the phbg its too lean so terrible quick throttle.

[kosmos]

Aug 11, 2023 11:44:20 GMT -5 br4inl3ss said:

UPDATE:
tested fuel delivery, same shit happens. no difference at all.
fuel delivery is fine.
and it wasnt any better after more testing testing ( before testing fuel delivery ).
it just seemed better but wasnt.

waiting my main jets, but they are ofcourse not the cause of the problem.

thats so damn weird... with cvk's they're too rich so terrible quick throttle, and with the phbg its too lean so terrible quick throttle.

when your ripping the throttle back and its cutting out immediately, its your pilot, mixture screw, or an air leak