Oh Boy, fighting the jetting fight......:(

VMAX  Forum

Help Support VMAX Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

TourMax

Well-Known Member
Joined
Apr 22, 2018
Messages
64
Reaction score
0
Location
Cambridge
My bike is a Venture and Vmax Hybrid. In a nutshell: Vmax engine in a Venture.

d51155df06324ec3841e44594f28de25.jpeg


Compression is good (160-170 psi) and valve clearances set. carbs are clean (ultrasonic bath).

Airbox is a flat panel insert since the VBoost manifold made the stock venture airbox too tall to fit under the cover/faux tank. Basically, too a slice out of the OEM airbox and made a flat panel adapter, then built a cover for the flat panel. The airbox opening is bigger, but not overly so. Probably not making figuring out the jetting any easier, but it doesn't make it impossible.

Exhaust is the stock venture headers and collector with a couple R1 mufflers. Little extra flow, but not much more.

With 37.5 pilots, needs 3.5/4.5 turns out to get CO at 3.5%. So they're too small.

Tossed in a set of 42.5 jets. That's all 1 turn or less to get the CO at 3.5%. So too big.

HAve a set of 40 pilot jets on order and we'll see what we get. Logically, 40 is square in the middle between 37.5 and 42.5 so that should put the mixture screws right in the middle around the 2-2.5 out mark.

The 37.5 pilots actually allowed it to run decent, until hitting cruise speed at the 1/8 throttle (approx 50 mph). Then it started breaking up and missing. My needles are adjustable (OEM) and raising them one notch vastly lessened the tendency to miss at cruise.

I never got to riding it with the 42.5's as it was very touchy to even get the Co within spec, the carb balance stable and rpm right. You could literally just touch the mixture screw with the screwdriver and change the CO readings to way lean. Just too touchy all around.

Also found the wet float levels are a little low (18-19 mm), I plan to bring that back up to the 16-17mm mark.

Hopefully, the 40's put the mixture screws in the right range to fatten up the transfer ports enough that cruise doesn't go lean like it does with the 37.5's and lets me keep the needles close to center adjustment.

Then, figure out the mains. Should be easy (famous last words!) after this quagmire is sorted....
 
You need air correctors!

Air correctors?

Pilot air jets maybe?

If PAJ1/2, can you give an idea which way to go? They're the stock PAJ's right now. I'm guessing PAJ2 smaller since it's exhibiting lean miss at cruise?

Edit: a quick look at "parts fish" reveals same PAJ2 (170) for vmax and venture (1986). But PAJ1 is an 80 for venture and 90 for vmax.

Seems counter-intuitive to go larger on PAJ1 when it's exhibiting lean miss conditions?

edit 2: I thin I cocked that up and looked up the main jet instead of PAJ1...
 
So once again, google is my friend.

Seems air correctors compensate for it being a fixed jet.

Looks pretty like a simple press it in deal and have found some forum threads on it.

Maybe i’ll fire up the lathe and make some brass chips. Seems from another forum thread a .020 orifice is the size needed. I can play with that later on once i get it running decently.

Or i could do another way i read about threading the port and using small bs30/97 series jets...
 
I have them available for $15 plus postage for the set of 4.
 
I have them available for $15 plus postage for the set of 4.

Thanks.

Im going to try and spin up a set so i can try it out. Buying and shipping would take another week and i’d like to get it done sooner than that if i can.

Pretty simple little project really. Couple bucks in brass rod, get the OD right and proper precision drill to give the 0.020 it looks like they are made to. Might even make them screw in, just for convienince sake and offer some additional “tunability”.

If it all goes to shite, i’ll get in contact via your website and order a set.
 
Well, when the third precision bit broke off in the brass and my steady rest cracked, I decided it just wasn't worth the aggravation.

It doesn't help that we just moved into a new house (retiring, last house...ever) and my tools and materials are all over the place and/or still half in boxes. Doing anything in the garage is an exercise in frustration right now, let alone trying to machine something with any precision.

So I'm tossing in the towel and ordering up 4 correctors from Morely's.

Order inbound....
 
Just FYI, the pilot jets are basically in use from 0-4000 rpm, at about 1/8th of the throttle. If the stock springs are used (7 inches), then the needles should should start over lapping in the 4000 rpm range, with the pilot jets.
 
So, not being successful at making the air correctors was sticking in my craw.

So had another go at it today and:

cd14cbd94bc849bf8aca25139beba367.jpeg


4b12fe929dd144588dbb4743dda55358.jpeg


Machined to press fit tolerance for each port, chilled and then dropped in. Nice and tight when temp notmalized with carb body. Passage is .020 in each corrector, as I read in another thread. Step in the top to make pulling them out later possible if need be.

I still have a set of correctors on ordered from Morely, just in case these dont work out properly.

:)
 
Just FYI, the pilot jets are basically in use from 0-4000 rpm, at about 1/8th of the throttle. If the stock springs are used (7 inches), then the needles should should start over lapping in the 4000 rpm range, with the pilot jets.

image.jpg


;)
 
Another note when testing. You MUST have not only the airbox in place (along with the filter) but you must ALSO have the body cover in place or you will get a very false reading. By the way, here's one Venture/Vmax project we did.

We used the 1300 bottom end, Vmax Heads/Cams, RS Tour Deluxe 5th gear with Vmax 1-4 gears. Vmax Rear Diff. Custom full header, Muscle Jet kit. Carr Wheels, Big brakes, and a whole lot more.
 

Attachments

  • IMG_20150418_150836_569.jpg
    IMG_20150418_150836_569.jpg
    55 KB · Views: 32
  • IMG_20140328_171908_654.jpg
    IMG_20140328_171908_654.jpg
    69.2 KB · Views: 32
It was getting late, so i only had time to get the carbs back on and run it a little bit.

Only got to check 1 and 2, but intial CO adjustments seem to be much more predictable and in the 1.5-2 turns out range with the 42.5 pilots. HC seems to be better as well, but still a bit high. I don’t nt spend a lot of time adjusting though. Sync adjustments seem much less “touchy” as well.

Thinking abut about it, the open panel filter infreas d volume but would have eecreased velocity. That resulted in a lower vacuum signal over the idle circuit, which lead to inferior mixing of fuel and air. The restrictors (ie: correctors) recreate that stronger signal by providing a restiction in the main air cicuit and recreation the lost velocity.

Makes perfect sense when i think on it.

Now to get it set up and out for a road test to see if my lean miss at cruise is resolved.

Then on to plug chops.....again.

:)
 
Another note when testing. You MUST have not only the airbox in place (along with the filter) but you must ALSO have the body cover in place or you will get a very false reading. By the way, here's one Venture/Vmax project we did.

We used the 1300 bottom end, Vmax Heads/Cams, RS Tour Deluxe 5th gear with Vmax 1-4 gears. Vmax Rear Diff. Custom full header, Muscle Jet kit. Carr Wheels, Big brakes, and a whole lot more.

Yessir, i watched your posts as a you built that one with great interest.

I check you comments on needing the airbox/tank cover, but mine isnt just an open flat panel. I built it with a “lid” that is kind of an “intake” facing forward. It was more about taming intake “honk” for those longer rides. It is a touring bike after all...;)

The lid is just in prototype form right now. Basically, whats left of the original venture lid with a cardboard shape on it covered with foil tape. Final form will likely be fiberglass, as I work in fiberglass quite regularly and am comfortable with it. Learned ‘glassing from my dad (rip) who used to be a shipwright.

I’ll try and toss a pic up when i get a chance if you're interested.
 
Always like to get pics of builds! Never know where there's a great idea that can be shared.
 
Finished up with balance and CO adjustments.

Buttoned it up and took it for a burn. The cruise miss seems to be gone. Power seems pretty good, perhaps just a little soft. Pulls pretty cleanly from lower rpms, maybe just the slightest amount of “chug”. But thats something i can sort out with a bit more work.

Vboost is absolutely ferocious when it comes in. Cross 5 grand (where i have it programmed to be full on) and it shoots to 9 grand almost faster than i can shift it. Theres no missing it, its an obviuos audible change and the bike actually “stands up” on its suspension when the power hits. I used to race RD/RZ’s when i was younger and this is almost like a 2 stroke coming on the pipe. Kinda neat feeling, for a big touring bike.

It even pulls the 5th overdrive from 2 grand, with either throttle or the cruise control. It gains speed and rpm slowly, but its a pretty deep overdrive so that makes sense (hasa vmax rear diff and 2002 royal star transmission).

So it seems my “diy” air correctors are doing thier job.

At least now that it is running decently, i can work on refining the carbs to a better state of tune.

:)
 
Last edited:
So, rode it to work today. About 65 kms total. Some back country road (80 klh) some highway (100-110 kph).

Needs just a graze of choke to start and then will idle low and lumpy with choke off until it gets some heat in the block. Keep the choke on and settles in nicely to a fast idle.

Ride to work pretty much stays at 1/8 throttle, 1/4-1/2 at most. So i’m mainly running on pilots and the transfer ports all the way. Highway needs 1/8-1/4 throttle, but headwinds were strong and gusty today.

Pulls pretty decent everywhere. Still feels a maybe a touch soft. Might be a bit slightly rich. This weekend i may hook up the 5 gas again and see where its sitting for CO and HC. Still might try the 40 pilot jets. Probably worth it to change out the jet block gaskets as mine where a little chewed up. Still in decent shape, just not the optimum.

No carb pops, no exhaust pops, no popping on decel.

Seem to be an occational light cruise miss that comes and goes. Mostly not there, but i willl catch it doing it occasionally.

So still a little work to do.

When Sean’s correctors get here, i think I will pull mine out and drop those in to see if anything changes. If it grts a little better, I’ll leave those in and start tweaking the jetting again.
 
Jeez, 82 bucks cdn for 15 usd air correctors to my mailbox after everyone took thier pound of flesh!

I suppose i could have gone a bit cheaper in shipping, but canada post looses stuff on a good day so i wanted to make sure they got here in a reasonable amount of time. Well, that it gets here at all too! Lol!

Sometimes, it sucks ordering parts in Canada...you gents south of 49 dont know how good you have it (in some ways).
 
Also found the lovely surprise that the pull cable below the cruise splitter is fraying.

There went another 70 bucks.....:(
 
Alrighty.

Bike is running decent, fuel consumption seems pretty high.

Filled it this morning. trip is now at 75 kms. Tank is going to hit the half mark in about another 10-15 kms at this rate.

Thats going to fall out in mid to low 20mpg range.

Thats all light cruising, no vboost at all.

Yep, something is def not right here.

I’ll pull the plugs shortly and have a look. If theyre fluffy black, that will tell me what i need to know....
 
Last edited:
Well, plugs actually just confused me more. The pattern and colors made no sense at all with the running characteristics.

So went back and hooked up the 5 gas.

And then things went all catty whompass.

Fuel screws ended up around 1/4 turns out again. Complete 180 from last time.

Then it started being unpredictable across all cylinders. Both CO and balance.

I think i might be chasing an ignition problem. Reason being: i could get a good CO, HC and O2 adjustment, but for no reason #4 would shoot up to 1000-1500 ppm HC and not respond to fuel screw adjustment.

That would indicate an ignition problem of some sort. Ie: weak spark, timing, advance or retard, etc....

Spark plugs look good and a nice sharp spark jumps the electrodes on all of them, so I’m leaning towards something in the wiring, an ignitek issue or perhaos ignition timing.

Tomorrow, I’m going to r check the wiring on the COP’s and change the ignitek from “auto” to “short” and see what I get....
 
Last edited:

Latest posts

Back
Top