Exhaust like a shotgun

[VJohn]

So!
As it stands. My 2000 vmax hasn't been able to start for a good while.
When trying to start the engine it turns over but no go.
If this is kept up I believe the right exhaust lets of such a loud bang my cat legged it and I had ringing in my ears for good few mins .

I have stripped, cleaned and wet set the carbs within specs.
Checked the spark plug sparks and looking pretty!
But still the bike just turns and then the random heart stopping bang.

So I'm guessing what I'm trying to ask is what's a good checklist for a backfiring vmax?
Thanks for your future time!

 

[02GF74]

When you stripped the carbs, did you remove both jets from the jet block and clean them out? The pilot jet has a tiny hole that is easilyy blocked.

Mine, a Canadian model imported from Japan, had been satanding for a while and the pilot jets were blocked solid; when trying to run it would back fire through the carbs and exhaust, clearing them fixed it.

Have you checked the choke plungers return when released and presumably becasue you cannot get it to run, you have not balanced the carbs?

 

[Fire-medic]

When you stripped the carbs, did you remove both jets from the jet block and clean them out? The pilot jet has a tiny hole that is easilyy blocked.

Mine, a Canadian model imported from Japan, had been (sic) satanding for a while and the pilot jets were blocked solid; when trying to run it would back fire through the carbs and exhaust, clearing them fixed it.

Have you checked the choke plungers return when released and presumably (sic) becasue you cannot get it to run, you have not balanced the carbs?

This is what he means:

using a wire to poke-out deposits from the pilot jets


enrichener (choke) plungers are out of synch.

If you unplugged the ignition coils, be sure they are plugged in properly. In front, the left coil high tension lead goes to the right front cyl/sparkplug (#4 cyl.). The right coil high tension lead goes to the left front cyl/sparkplug (#2 cyl).

 

[VJohn]

When you stripped the carbs, did you remove both jets from the jet block and clean them out? The pilot jet has a tiny hole that is easilyy blocked.

Mine, a Canadian model imported from Japan, had been satanding for a while and the pilot jets were blocked solid; when trying to run it would back fire through the carbs and exhaust, clearing them fixed it.

Have you checked the choke plungers return when released and presumably becasue you cannot get it to run, you have not balanced the carbs?

I shall remove and slowly go through the carbs again and let you know.
I have been using a ultrasonic cleaner and carb solution so they did come up sparkly. Maybe I've still missed something. Thanks. I'll let know how get on!

 

[VJohn]

This is what he means:
View attachment 86290
using a wire to poke-out deposits from the pilot jets

View attachment 86289
enrichener (choke) plungers are out of synch.

If you unplugged the ignition coils, be sure they are plugged in properly. In front, the left coil high tension lead goes to the right front cyl/sparkplug (#4 cyl.). The right coil high tension lead goes to the left front cyl/sparkplug (#2 cyl).

View attachment 86291

Thanks for the details man!
The chokes are being pulled out in sync and returning well.
The backfire still occurs without choke also. I'm hoping it's me and I've not appreciated how meticulous need to be with the carbs.
I shall check the coils also. I've only touched the rear ones. And the bike has run before.
I'll keep in loop!
Thanks very much guys.

 

[02GF74]

I have been using a ultrasonic cleaner and carb solution so they did come up sparkly. Maybe I've still missed something. Thanks. I'll let know how get on!

I read about ultrasonic cleaning all the time but am not convinced it will clear a tiny hole (I estimate about 0.3 mm) especially if it is blocked solid.
My understanding is that ultrasonic cleaners create tiny explosive bubbles (cavitation) in the liquid but in the case of pilot jets, liquid cannot flow through the hole so the bubbles are attacking the small area that is the 'hole' at each end of the jet.... hence I am not convinced that this method works for blocked jets unless left in the bath for a very very long time.

As mentioned, in my case the jets were blocked with a quite hard material, to remove that, I had to file down a sewing needle to reduce its diameter and slowly chip away from both ends. To clean up the hole, I made small files from copper wire strands and aluminium MIG wire with crimps using a set of cutters to act as 'teeth', both metals being softer than brass so in theory should not enlarge the diameter of the hole.

I've since bought a set of carb cleaner files, like these, but yet to use them.



Re. enrichment plungers - check that they are free to return to closed position when choke is off - the left one has not returned - see the amount sticking out above the black rubber seal.

 

[Fire-medic]

Your pictured 'carb cleaner files' are merely oxy/acetylene tip cleaner rods. One of them should do the work.

As to ultrasonic tanks, yes to doing a thorough job cleaning your carbs. As 02GF74 mentioned, if you have hardened accretions/deposits, then a poke or two should take care of that. What I do after disassembly and the ultrasonic soak, is to see if the pilot jet (or any other passage) is 'see-through.' If not, the tip cleaners/'carb jet cleaners' get called into play.

I don't use the carb jet cleaners as they typically have a knurled circumference which if carelessly used, could result in damaging the diameter of the passageway.

This is what you should be able to see, a 'light at the end of the tunnel.'



I have a stainless steel brush with just the correct size bristles to clean the pilot jets, it's a 'lifetime supply' of pilot jet cleaning rods. I've mentioned before, a pin vise is just the thing to hold a thin wire for penetrating the blockage, with a twist of your thumb and forefinger to 'drill' through the crud. For instruction on how to do this, view the Steve Buscemi tutorial below:



A thread with additional helpful content:
https://www.vmaxforum.net/threads/2005-vmax-not-wanting-to-idle.51704/#post-521217
A close-up of the carburetor starting enrichener rods/pistons being 'way-out of whack:


This misadjustment is really-bad! A word of advice if you use an ultrasonic tank, if you do not remove the screwed-on casting which holds the enrichener piston, be sure to remove the gland nut that the enrichener piston shaft goes through, immediately after the carburetor bodies are removed from the tank, and use whatever spray lubricant you use to thoroughly douse the piston and the cylinder in which it moves. Failure to follow this advice will soon result in a frozen piston, and those bolt-on bodies are no-longer available from Yamaha.

 

[Smithjs35]

Great info on the ultrasonic cleaning. Preparing to do my carbs in the near future so I got one and have asked the question what to use for solution. Some cleaners almost acid etch which would definitely mess with the enrichener piston. Wife says to use dawn and I say carbs aren't jewelry though I seen some pretty ones.

 

[Fire-medic]

Dawn works but do not use it as a strong solution! Try it first on something you don't care if the color changes, as I think the Dawn may cause a change in the metal color. I give my parts to my friend and he runs 'em for me.

 

[wayne billings]

I had a nasty back fire as you described. I think it was a coil connector not fully put together. I hope you get it sorted.

 

[VJohn]

Your pictured 'carb cleaner files' are merely oxy/acetylene tip cleaner rods. One of them should do the work.

As to ultrasonic tanks, yes to doing a thorough job cleaning your carbs. As 02GF74 mentioned, if you have hardened accretions/deposits, then a poke or two should take care of that. What I do after disassembly and the ultrasonic soak, is to see if the pilot jet (or any other passage) is 'see-through.' If not, the tip cleaners/'carb jet cleaners' get called into play.

I don't use the carb jet cleaners as they typically have a knurled circumference which if carelessly used, could result in damaging the diameter of the passageway.

This is what you should be able to see, a 'light at the end of the tunnel.'

View attachment 86295

I have a stainless steel brush with just the correct size bristles to clean the pilot jets, it's a 'lifetime supply' of pilot jet cleaning rods. I've mentioned before, a pin vise is just the thing to hold a thin wire for penetrating the blockage, with a twist of your thumb and forefinger to 'drill' through the crud. For instruction on how to do this, view the Steve Buscemi tutorial below:



A thread with additional helpful content:
https://www.vmaxforum.net/threads/2005-vmax-not-wanting-to-idle.51704/#post-521217
A close-up of the carburetor starting enrichener rods/pistons being 'way-out of whack:

View attachment 86297
This misadjustment is really-bad! A word of advice if you use an ultrasonic tank, if you do not remove the screwed-on casting which holds the enrichener piston, be sure to remove the gland nut that the enrichener piston shaft goes through, immediately after the carburetor bodies are removed from the tank, and use whatever spray lubricant you use to thoroughly douse the piston and the cylinder in which it moves. Failure to follow this advice will soon result in a frozen piston, and those bolt-on bodies are no-longer available from Yamaha.

So here's a few things ticked off de list.
Pulled carbs apart. Believe I found all the jets l (in pictures).
The jet found inside the carb float chamber (in all the carbs!) were crudded up but released with blowing out with my mouth alone. Everything else was good!

The chokes look full closed so thats good.

Put back on the bike and try to start. Did have a puff of something similar to exhaust smell out of the rear right side carb.
Also still getting backfires. Checked the plug on this section and looking ok. Not black or white.

 

[VJohn]

So here's a few things ticked off de list.
Pulled carbs apart. Believe I found all the jets l (in pictures).
The jet found inside the carb float chamber (in all the carbs!) were crudded up but released with blowing out with my mouth alone. Everything else was good!

The chokes look full closed so thats good.

Put back on the bike and try to start. Did have a puff of something similar to exhaust smell out of the rear right side carb.
Also still getting backfires. Checked the plug on this section and looking ok. Not black or white.

Scrap that sorry. Bare with still learning carbs here issues with having bike almost as old as you.
I just clicked and googled the pilot jet. Didn't realise it's bottom inside of that unit inside the carb..... My bad... Round two ding ding!

 

[Fire-medic]

 

[02GF74]

it's bottom inside of that unit inside the carb....

That is the jet block. Inside are two jets, one being the pilot jet.

It can be removed without tearing the gasket, pull out the two rubber bungs then using the largest flat bladed screwdriver that fits into the hole, unscrew the jets.

 

[VJohn]

That is the jet block. Inside are two jets, one being the pilot jet.

It can be removed without tearing the gasket, pull out the two rubber bungs then using the largest flat bladed screwdriver that fits into the hole, unscrew the jets.

All bar one has come out. Looks like someones pre-mangled the brass head for me....

Even then, fluid and air still passes through it.
One was kinda grubby but again me blowing broke it up easily

 

[VJohn]

View attachment 86315View attachment 86320

View attachment 86321View attachment 86317

View attachment 86316View attachment 86319View attachment 86318

Loving these break downs. Thank you!

 

[02GF74]

Yeah, that doesn't surprise me. Now you've got this far, I'd still recommend removing the jets and running through the soft metal 'files' as mentioned above. I did, tapping the jet on a table until all the powder stuff stopped.. That way I knew jets were clear so the hole size was what the manufacturer intended.

Stuck jets have been successfully removed using a left hand drill - search the forum. Applying some heat should help get them out.

Re replacements, avoid the cheap Chinese knock offs on ebay, in this instance pay a bit more knowing that the jobs been done properly - again search here woes about these jets.

 

[VJohn]

Yeah, that doesn't surprise me. Now you've got this far, I'd still recommend removing the jets and running through the soft metal 'files' as mentioned above. I did, tapping the jet on a table until all the powder stuff stopped.. That way I knew jets were clear so the hole size was what the manufacturer intended.

Stuck jets have been successfully removed using a left hand drill - search the forum. Applying some Hest should help get them out.

Re replacements, avoid the cheap Chinese knock offs on ebay, in this instance pay a bit more knowing that the jobs been done properly - again search here woes about these jets.

Sounds good.
See if work got any needle files about. Probably will just get my own personal set though.

Yea I'll hunt down that removal now. Thanks!

 

[Fire-medic]

Yeah, that doesn't surprise me. Now you've got this far, I'd still recommend removing the jets and running through the soft metal 'files' as mentioned above. I did, tapping the jet on a table until all the powder stuff stopped.. That way I knew jets were clear so the hole size was what the manufacturer intended.

Stuck jets have been successfully removed using a left hand drill - search the forum. Applying some Hest should help get them out.

Re replacements, avoid the cheap Chinese knock offs on ebay, in this instance pay a bit more knowing that the jobs been done properly - again search here woes about these jets.

Speak of the devil:
https://www.vmaxforum.net/threads/h...-a-broken-screwdriver-slot.49066/#post-489249
See post #4:
https://www.vmaxforum.net/threads/c...gins-to-slip-when-hot-only.50163/#post-503170

 

[VJohn]

Hey guys!
Sorry it's been a long time since post. Lotta things going especially lack of cash flow!

I have worked on the bike most of time I can give with thanks to the information you guys have.

The carbs have been rebuilt. New jets and diaphragms. Even used unconventional method to test they are giving out fuel .

Found split rubbers on inlets so they were also replaced.
Still no starting...
Tried a method of putting fuel down the inlets had the bike running for 5 secounds. Have not been able to recreate this since.

The next thing we're on now is, with all the spark plugs out and testing one at time we are getting good sparks. BUT. If you leave the spark plugs in place and pull out and test individually the sparks coming from it are inconsistent. Which is bizzare.

Any ideas from you fine gentlement?