What jets and where from!

[edharrison]

In an effort to eliminate my 4k rpm stumble I want to get the best main jet for my setup:

Canadian 97 full power VMAX

Stock intake / airbox

Supertrapps closed cap 10 disks

Front downpipes changed to larger bore stainless - no crossover

Standard rear downpipes

Stock needles shimmed two washers at present


147.5???? Im in the UK so any ideas please?

thanks Ed

 

[CaptainKyle]

I have them on hand but you might can find them cheaper local by the time you pay the shipping.

 

[edharrison]

Thanks Kyle - do you think 147.5 is right for the setup?


Ed

 

[naughtyG]

Front downpipes changed to larger bore stainless - no crossover

Standard rear downpipes

I'm a bit stumped by that! Bigger front pipes but standard rears? Sounds like it would screw with the exhaust balance to me. Could you check out the diameter of your front headers as opposed to the rear ones?

I have a feeling your front headers are actually the same (at least internal) diameter as OEM, just they are stainless which means they won't rust.

Also unless they are standard diameter, the slip-ons wouldn't fit!

 

[edharrison]

They are the diameter of the double skin OEM all the way to the last 2" where they narrow to accept standard fit silencers or slip ons but they are single skin to much larger internally until the ends

http://www.ebay.co.uk/itm/V-MAX-120...92?pt=UK_Motorcycle_Parts&hash=item231a34a504


Ed.

 

[CaptainKyle]

Thanks Kyle - do you think 147.5 is right for the setup?


Ed

147.5 generally work pretty good with this setup.

 

[naughtyG]

They are the diameter of the double skin OEM all the way to the last 2" where they narrow to accept standard fit silencers or slip ons but they are single skin to much larger internally until the ends

http://www.ebay.co.uk/itm/V-MAX-120...92?pt=UK_Motorcycle_Parts&hash=item231a34a504


Ed.

That's a really interesting exhaust. I wonder why they would make it bigger only to restrict it at the ends!? And, the rear cylinders remain fully restricted too.

Does anyone here have any idea what this larger diameter 'until the slip-on bit' and on front headers only would do to performance? Is it equivalent to OEM because of the end restriction?

And, I wonder if this could be contributing to your cruise stumble.. :ummm:

 

[edharrison]

Sadly it was the same with the standard headers, I will do the shotgun with the compressor in the morning and update, thanks.
Ed

 

[naughtyG]

Fingers crossed.. If you get stuck I'm in Bristol for a couple of months, will pop over to London a few times so if you wanted to take the carbs off and go through them I'd be happy to help. You'd need to get the parts first though, or we couldn't get it done in one go. Only prob is until you open them you don't really know for sure what you're going to need..

Btw do you have a carbtune or similar to balance your carbs, and if so when did you do this last?

 

[edharrison]

Hi,
So kind thank you - I have balance gauges, done the shotgun again today very thorough with carb cleaner and compressed air, returned needles to stock and A/F to 3 turns to get a "baseline".

Sadly one thing I noticed was the holes that the needles go in (emulsion??) are slightly oval!!!

Ed

 

[edharrison]

Well after much effort the MAX is now in the capable hands of PDQ Developements, these guys are known to be experts on the Max since the eighties in the UK. Fingers crossed it will be done in a day or two complete with a Dyno sheet.

Ed

 

[edharrison]

Heres the result of the carb strip / clean and Dyno at PDQ, my problem is stuttering at steady throtlle between 3000 / 5000 rpm - notice the dip in the A/F is right where the issue is. According to PDQ this should not be a problem though....

Ed

 

[naughtyG]

So have they fixed it? To me it seems something's still wrong if the A/F looks like that in that area. Are you sure you have OEM needles in there?

 

[edharrison]

Hi,
No its not fixed sadly, PDQ said theres nothing wrong with the carbs - standard needles for sure, the bike is a Money pit!!

Ed

 

[naughtyG]

I don't think I can agree with PDQ - the dyno sheet shows that very clearly! I'm sure others with more experience than me in tuning and A/F ratios will chime in.

TBH I would go back and say sorry but no - that's not normal so please fix it or money back! Do you know anyone else with a Max? Easiest way to find out for sure would be to swap the whole carb rack and see what happens.

 

[edharrison]

I called them and they were not too interested, they said not to take much notice of A/F!

Im not into confrontation but a bit miffed at "the best in the country" pretty much saying thats it...if they are the best Im lost.

Love to hear any ideas when you guys look at the dyno sheet?

Ed

 

[naughtyG]

I think they just can't be arsed finding out what's up. Defo not 'the best' in my book..

How far have you gone in washer size in shimming your needles so far?

 

[edharrison]

Tried 0.4mm and 0.8mm as well as standard, just richens the mid range a bit. Cant think why the dip only happens there, it seems between the pilot and needle transition but quite severe.

Ed

 

[naughtyG]

It is totally possible for a part to be worn in there.. Did you say you found some holes were oval rather than round? This could be it - was it the jets? They're easily replaced and plenty of guys here may have some to send you cheap.

 

[Miles Long]

Heres the result of the carb strip / clean and Dyno at PDQ, my problem is stuttering at steady throtlle between 3000 / 5000 rpm - notice the dip in the A/F is right where the issue is. According to PDQ this should not be a problem though....

Ed

Ed-
If these people are "experts on the Max since the eighties" they must have lots of V-Max dyno sheets they could show you, probably some even with your exhaust setup. Chances are that none would show the dip in A/F as yours does. Wouldn't this be proof that yes,indeed, there is a problem?
It's hard to fathom why a reputable shop would deny the relationship of their dyno result, with the stumbling you are experiencing. It's right there, in black and white.........