new member with carb problems

[bikeman]

hi guys.


just joined the forum. I can't find a new members section. so I will get straight to the point.  I am and have been for the last 2 years building a one off special. it is just about complete but I am having trouble getting the carburettors set up .  


what it basically is. is a modified EX 500 frame. with a Vulcan 500 engine. with most of the parts sourced being off the 454. the main issue is because the EX has a unitrack suspension yet the bike is an out and out cruiser. because of the configuration of these two elements. no air box off any model will fit. I am therefore committed to using pod filters.  which I cannot  get to run properly.  


I have tried to glean as much info as possible on using pods on the 34CVK carbs but everything comes up short. so far I have tried.  blocking part of the filter to cut down on air flow. no effect. increased jet sizes to 140 main 40 pilots. the carbs [off a 454] had a smaller slide hole this has been increased to 3mm the needles lifted between 3/9mm and the carbs tuned in with the aid of a colourtune to seemingly get the mixture pretty near spot on but still it has issues.


starting and tick over is spot on rev engine 1/3 throttle it starts to stumble at half throttle it bogs down so bad it is almost like it is running out of fuel. yet if you get it passed this point .  it pulls like a donkey right up to balls out. soon as I shut off and try to increase engine speed it stumbles again.

is there anything you guys could suggest I try next. there is obviously something wrong but it has me stumped completely.
oh I must add it seems as though  the engine is over fuelled it stinks of fuel when run the floats are spot on and there are no leaks.

I have read as many pages as I could on the forum and I read you guys have had good success from fitting pods on these carbs so it must be possible I just have the feeling I'm missing something somewhere.

any ideas guys. thanks in advance.
col.

[Blaine]

Only thing I can think is your MJ is to big....Or needle to high.....Remember the needle controls 1/4 to 3/4 throttle.

[bikeman]

I'll try the 135 MJ I can't see it being the needles because I did try it first with one 3mm washer as I read in another thread. then two and finally 3.  I think I have done just about every other thing I have read about on line.  the thing is while it is stood it revs up no problem sounds really good and smooth but as soon as it is under load it won't rev mid range.

I also read somewhere that weakening the diaphragm spring can work but not sure what effect this would have.  as I understand it the main issue of fitting pods to CV carbs is that you lose the partial vacuum from under the slide diaphragms created by the air box. this is the cause of flutter and the slides not lifting smooth.  and the whole reason bigger jets and modifications are required.  I would have thought that increasing the spring tension above the slide was of more benefit as this would slightly compensate for the loss underneath.  or have I got that wrong.

[Blaine]

Nov 25, 2017 17:15:54 GMT -6 bikeman said:

I'll try the 135 MJ I can't see it being the needles because I did try it first with one 3mm washer as I read in another thread. then two and finally 3.  I think I have done just about every other thing I have read about on line.  the thing is while it is stood it revs up no problem sounds really good and smooth but as soon as it is under load it won't rev mid range.

I also read somewhere that weakening the diaphragm spring can work but not sure what effect this would have.  as I understand it the main issue of fitting pods to CV carbs is that you lose the partial vacuum from under the slide diaphragms created by the air box. this is the cause of flutter and the slides not lifting smooth.  and the whole reason bigger jets and modifications are required.  I would have thought that increasing the spring tension above the slide was of more benefit as this would slightly compensate for the loss underneath.  or have I got that wrong.

Thats how I did mine...I cut 3 coils off the spring & it worked perfectly...Never had to drill the slide.

[bikeman]

thank you very much for your help at this point I'm prepared to do almost anything because I'm really stuck.


been at these carbs now almost a month.  and tried just about everything.  I think one of the problems is I'm using 454 carbs on a 500 engine. 

so the usual [if there is a usual] fixes don't work.  most of the mods to the carb set were to bring them up to 500 spec. the needles are different the jets much smaller the holes in the slides smaller ect ect.  I think this made the matters a whole lot worse.  because I had to go much bigger than you lads with 454's would consider.


the 500 uses 130 mj and 35 pilots the holes in slides are 3mm and the needles are more aggressive for the first 3/4 from the point.  now to bring the carbs up to spec for the 500 I fitted 500 EX needles made the holes the same size and fitted standard 500 jets. popped the pods on and of course I had no chance. 


so after much research decided to go bigger to compensate as this was regarded as the way to go. by increasing the size of the jets by one size it didn't work.  so went another size. still no good . so I tried blocking off some of the pod area as some said this works by fooling the carbs it still has the air box. doesn't work. no matter how much is blocked off. then tried to fit stacks as some said turbulence was the issue.  didn't work either. so that left lifting the needles. first by 3mm then 6mm then 9mm this gave the best results [while stationary] it seemed to run ok. colourtune said the mixtures were spot on at all throttle positions. so because I could not ride it until finished got on with the rest thinking the pods were sorted.

1st mistake. don't assume anything. on getting it on the road I rode it very carefully for the 1st 100 miles at low throttle it ran perfectly. then went to open it up and it bogged down.  

since then I have tried every combination of the jets and needles I have some it made it a lot worse . some a bit better but it still bogs down. 

will try cutting the springs down next with standard 500 kit and see what happens. then try the 454 kit.  it must be possible pods have been used on everything  from 250's to 1000's all with cvk's and although the methods may vary most seem to work.  although to be honest most never say exactly how it was done just  the odd prod in the right direction. 

[eaglerider]

AHA!!!!!! There's the problem!! I also have a 500 engine, and used the 454 carbs with larger main jets.....Not a good combination, I found out. 454 carbs are 34 CFM....I found a set of 2002 or 2004 ( I don't remember the year) 27 CFM carbs, and used 140 main jets, ( as I have competition cams in my 500, older model Hardly D mufflers, no crossover pipe. I know, 37 CFM does not sound like much more than 34 CFM, but it made all the difference in the world. My 500 engine is a 94 Ninja 500, with the chain drive changed to belt drive. But that is another story.

[bikeman]

AH "Huston we may have a problem up here"  I had no idea there was a difference. sounds logical though.  not sure what to do next. more carbs is more expense and then more kits ect, I will try the last couple of options then if it's still a no go may resort to plan "B" and buy flat sliders.  shame really as I though I was so close to a resolution.

[eaglerider]

You don't need the kits, you already have the jets. look on ebay for the carbs.

[bikeman]

Nov 27, 2017 7:22:30 GMT -6 eaglerider said:

You don't need the kits, you already have the jets. look on ebay for the carbs.

yeah fair comment the kits are new also so should not be an issue. now for the nitty gritty [as the English would say]  exactly what do I have to do to these carbs to get them to run on pods. I know this is a loaded question because I have done so much to the other [454] ones without success.  what's required and what isn't.
it would be a pity to buy more carbs and end up with the same results and have two sets of non running CVK's.   the flat sliders are a lot more expensive to buy so would prefer a cheaper option as the bike has been so expensive to build up to now but it has to be able to run on pods as I said before. 

thanks
col.

[backofthepackjack]

Plug check, This will take guesswork out of the equasion.

Take the bike out for a run if your able to do so and make it run for a mile or so right at the rpm where it hates to run and keep the rpms right there. then hit the kill switch and pull the clutch in and coast to a stop. pull the plugs and do a plug reading. it will be very evident by the colour of the plug  wether you have a lean or rich issue. Then you will know which way to tweak the jetting

[bikeman]

Nov 29, 2017 12:22:28 GMT -6 backofthepackjack said:

Plug check, This will take guesswork out of the equasion.

Take the bike out for a run if your able to do so and make it run for a mile or so right at the rpm where it hates to run and keep the rpms right there. then hit the kill switch and pull the clutch in and coast to a stop. pull the plugs and do a plug reading. it will be very evident by the colour of the plug  wether you have a lean or rich issue. Then you will know which way to tweak the jetting

thanks for the tip. unfortunatly it won't run a mile. above 1/3 throttle unless you whack it right open. the engine just dies within 50 yards. also there is no chance of getting to the plugs at the side of the road.   it has cops fitted and the thermostat housing is off a ER [on top of the head] the seat. tank. top hose and top mount for the tank has to be removed just to get at the coils. [not my brightest design feature] but it wasn't supposed to be fixed at the side of the road.

since my last post I have reduced the mains to 135 cut 4 coils off the springs [first two then 4 when there was no improvement] bike still does not run as soon as the mains take over I have tried lifting the needles by yet another 3mm and also without any shims still is a no go.
 
just about ready to give up on this carb set up now. unless some one has any insight as to where I am going wrong. it could work. should work. but doesn't.  
is there anyone out there prepared to explain how they got there bikes to run pods. what modifications did they do and was there any pitfalls I should be aware of.

I hate admitting defeat but this is beyond me. close but no cigar comes to mind.  

[Blaine]

Most were not trying to run 454 carbs on a 500 engine.....I think Eagle is spot on.........Also just a stab in the dark.....you have the 500 flywheel on the 500 engine & electronic box?

[bikeman]

hi. yeah the complete set up is straight off a 96 EX. all the electrics ect, except for the coils [these are zxr 600 coil overs]. on top of iridium plugs.  the engine is 94 EX also.[tell by the engine numbers]  I bought it out of a EN500 but it wasn't the original engine but a replacement EX unit with the shiny bits transferred. so has the sportiest cams. and black widow 2 into 2 exhaust.  all the cooling system is straight off a ER 500 except for the radiator [EX] as it would not fit the frame.

ironic as it may seem I only went for the 454 carbs because of the chrome tops.  I will search the local breakers for a pair of EX carb bodies to transfer the kits onto otherwise will order the flatsliders instead as I know these will work.

I am no stranger to carbs or a novice just stumped on this set up. what I do know is the bike runs great up to 1/3 throttle. so the pilots are right. it also goes like a train above 3/4 throttle so the mains must be near enough also.  it is the mid range that's the problem.  that should be down to the needles or slide action. but no combination I have tried seems to work.  I understand the difference in the flow rate. and if the engine ran ok but only produced a lower BHP at full throttle then I would assume the smaller bodied carbs were to blame but it really pulls strong at full throttle. I would have thought this is the area most affected by lower flow rate. 
I could be wrong of course it just seems logical.

[Blaine]

I agree....Now I'm stumped. Lol

[bikeman]

hi all.


I have tried all the breakers we have and not been able to get any 500 carbs. spent the rest of the day altering things around without any success. so I'm going to bite the bullet and buy some sliders.   the project depends on using pods so there seems little choice in order to progress further.


thanks to all those who tried to help. when I get it running I will post a how to. it may be of use to others who have gone through this ordeal without achieving a good outcome.  there must be plenty of those out there.

[bikeman]

hi all. just to round off this thread and report on the conclusion. I finally crack it after many weeks of experimentation.  it occurred to me that eaglerider had something with the idea of wrong flow rates. everything seemed fine except it didn't run at all well. I had read somewhere about lambda flow though CV carbs being critical [one reason for the airbox] and turbulence  under the slides. so I made up a pair of velocity stacks between the pods and the carb throats.


I made them 4in long [throat diameter X2] out of some silicon tube with 2in plastic pipe insert [to mount the pods on]  instant success the mid range came back smooth even it took some time to readjust the pilots and find the right main jet for the new set up but it works just fine now.  it turned out the 454 needles were better than the ex ones as the profile wasn't as aggressive and gave a smoother transition from low revs to higher mid range.


I don't think it is as powerful as it should be. [the ex500 has 60 bhp] at the  top end but that doesn't matter as it is a lot smoother in the working range of 6/8k so very happy to leave it at that.  there is nothing more frustrating than getting so far yet not being able to find that missing element that makes it all work.

thanks for all the help guys.