Throttle Balance adjustment

[GodOfDirt]

Originally Posted by Scootergptx

I think I'll look into this on mine. Just to be sure, do you mean plugged, or plugged together as in hooked up to each other?

Sorry, yes I connected the two together. I would like to runn the map off a tee next time im in it.

[GodOfDirt]

Originally Posted by gv550

I think your differential manometer is indicating a serious intake manifold leak, rather than an out of adjustment throttle body. The manifold can leak air at the cylinder heads, injector ports and at the throttle body.
The manifold to cylinder joint is a bit cheesy, and I sealed mine with Hylomar on the aluminum surfaces, made a world of difference in how the bike runs. I also added sealant to the injectors and installed the Thunder gasket at the throttle body.
In theory you may be able to compensate for a manifold leak by adjusting the idle air screws, but the engine will still be pulling unfiltered air past the leak, and the leak gap may change with engine temperature.

That was my first thought. I smoke tested the intake looking for large leaks first. then sprayed ether while running looking for small leaks. all checked out. I plan on getting the thunder gasket ( or make one).

[GodOfDirt]

Originally Posted by RACNRAY

I agree Garry..It is such a well known fact of the intake leaks on the 1700's. God of dirt I thank you for startin this thread as it compelled me to do 2 things on my skoot.

First was to check the idle vacuum balance. Using my carb stix there was LESS than a 3 mm difference between the 2 cylinders. Adjusting these even made no discernible difference, but I as most have done have sealed my throttle body to intake manifold junction, and on top of that the junction of intake manifold to the heads, another prime source for vacuum leakage. Safe to say I have no vacuum leaks to have a negative affect.

Second I always knew but never gave it much thought that the MAP sensor is fed vacuum from just the rear cylinder, all of the 4 cylinder skoots have vacuum ports on each t/b that connect into a common hose that feeds into the MAP sensor. DUH ME!!! So last night I machined an extra vacuum nipple outa stainless steel, drilled out the throttle body and pressed it in. This extra nipple feeds into a hose which tees off to the rear t/b and both feed the MAP sensor. The one existing nipple on the front t/b bore can be used to accomplish this tie-in, but I wanted to make future checking of the idle air vacuum a bit simpler.

Idle seems a bit more stable so I will have to wait until I can ride the skoot to determine any on-road differences.

RACNRAY

No problem, I'm good at stirring pots. I like the idea of adding another port. I did get that extra tb. I have done about 900 miles since I adjusted the mix and still running strong. I plan on tearing back into it to look for leaks and recheck the balance.

I need to find some local with a vulcan to do some comparing. now I'm going to start on that hiway instability.

[RACNRAY]

ELL...connecting the MAP sensor proved to REALLY, and I mean REALLY INCREASE the vacuum signal to it and SEVERELY richened up the air/fuel ratio, enuff where the skoot ran like crap and was drinking gas like it was free!

I firmly believe in having both cylinders feed vacuum to the MAP sensor but this will require a MAJOR retune, and I'll have to check this out when I can get it back on my dyno.

For now I'm just gonna plug up one hose to get my performance and mpg back!

RACNRAY

[GodOfDirt]

Hmm that's interesting. Are you running a chip?

[RACNRAY]

Originally Posted by RACNRAY

ELL...connecting the MAP sensor proved to REALLY, and I mean REALLY INCREASE the vacuum signal to it and SEVERELY richened up the air/fuel ratio, enuff where the skoot ran like crap and was drinking gas like it was free!

I firmly believe in having both cylinders feed vacuum to the MAP sensor but this will require a MAJOR retune, and I'll have to check this out when I can get it back on my dyno.

For now I'm just gonna plug up one hose to get my performance and mpg back!

RACNRAY

WELL...learned a bunch bout the FI system on this experiment. I did not feel like pullin the tank off to get to the vacuum hoses so I just propped the back end up and reached in to pull the hose off the rear cylinder t/b bore vacuum fitting and plugged it up, keeping the front cylinder t/b bore connected to the MAP sensor.

Started the skoot up, it ran for 8 seconds then shut off. I could restart but it wouldn't stay runnin, couldn't even get it outa my shop. This time pulled the tank off, put everything back to stock (rear cyl connected to MAP sensor) and wala...runs normally. Since the MAP sensor is not connected to multiple cylinders it receives a vacuum signal only once every 2 crank revolutions (when that rear cyl is on it's intake stroke), that equates to one voltage signal at the ECU which is obviously timed for the proper firing order of injectors and ignition timing. At least I found out that with my properly sealed intake system my idle imbalance was miniscule, not even enuff to make any difference. Nice to know.

Originally Posted by GodOfDirt

Hmm that's interesting. Are you running a chip?

A WHAT?

RACNRAY

[GodOfDirt]

i meant to ask if your running a programmer or tuner or some other type of signal modification device. i have some rubber plugs in the freezer to make some vacuum adapters for the intake runners to test seals. not pleased with the fact i have to test all this with less than 2000 miles on the bike because the 120lbs dealer mechanic says it runs fine across the parking lot. the whole reason i bought a metric was be able to jump on and ride. looks like maybe i got a lemon.

[RACNRAY]

Originally Posted by GodOfDirt

i meant to ask if your running a programmer or tuner or some other type of signal modification device. i have some rubber plugs in the freezer to make some vacuum adapters for the intake runners to test seals. not pleased with the fact i have to test all this with less than 2000 miles on the bike because the 120lbs dealer mechanic says it runs fine across the parking lot. the whole reason i bought a metric was be able to jump on and ride. looks like maybe i got a lemon.

I am runnin a PCV.

Check out this link to my thread on intake leaks done back in 2011. Do the mods (except the machining on the manifold and t/b as the Thunder intake gasket (not available at that time) is the new fix. Tightening up the 3 t/b bolts do nothing for crushing the orings as the stand-offs on the t/b prevent proper o-ring crush. Virtually everyone that has installed the gasket has had positive results and I would HIGHLY recommend you re-check ur idle balance.

RACNRAY

[UNCLE WILLIE]

the screws on the throttle body only balance the air flow at idle speed when the throttle plates are closed..use a guage to adjust not your ears or imagination ... that idle circuit should have no effect on anything the engine does beyond idle

[Scootergptx]

I'd like to get a thunder gasket, but just checked and it was $16.27 to send a $6.49 part.

[gv550]

Originally Posted by Scootergptx

I'd like to get a thunder gasket, but just checked and it was $16.27 to send a $6.49 part.

They adjust the shipping to the actual cost after you place the order.

[Scootergptx]

Originally Posted by gv550

They adjust the shipping to the actual cost after you place the order.

I'll probably just call them. Done that with some part places before and the guy taking the order says the stuff I want fits in an envelope. Shipping on that went from 12 bucks to 2.

I don't mind paying for shipping, but as long as it's realistic.