Starved?

[jonmasaya]

Hi all, just wanted some folks to check my reasoning on this one.

Just finished installing the dynojet stage3 kit on my carbs after installing pods and 4-1 exhaust on '82 750EZ. it rips and runs awesome, until... I get up on the freeway.

Right around 60mph the engine pulses and hesitates to accelerate. Eventually, after running at that speed for some time, it loses power and dies as if it was out of gas. Switched to "PRI" and it will keep going without dying, albeit a jerky, scary ride. (I discovered this yesterday, on Christmas, on a 30 mile drive up an icey mountain highway... no fun)

I'm thinking this is a petcock issue. The new jets are asking for more fuel than the petcock can deliver and the engine is starving out, right? I'm sure it's about time to replace it anyways.

Suggestions on good places to order a new one?

 

[posplayr]

Hi all, just wanted some folks to check my reasoning on this one.

Just finished installing the dynojet stage3 kit on my carbs after installing pods and 4-1 exhaust on '82 750EZ. it rips and runs awesome, until... I get up on the freeway.

Right around 60mph the engine pulses and hesitates to accelerate. Eventually, after running at that speed for some time, it loses power and dies as if it was out of gas. Switched to "PRI" and it will keep going without dying, albeit a jerky, scary ride. (I discovered this yesterday, on Christmas, on a 30 mile drive up an icey mountain highway... no fun)

I'm thinking this is a petcock issue. The new jets are asking for more fuel than the petcock can deliver and the engine is starving out, right? I'm sure it's about time to replace it anyways.

Suggestions on good places to order a new one?

Right ; sounds like the petcock. Z-1 has OEM like replacements. A thread about these recently.

Good job on jet kit. Should run to redline without any hesitation

 

[Guest]

What jets and which notch on the needle did you use?

 

[SqDancerLynn1]

Make sure the fuel tank vents are working

 

[Guest]

Is there an in-line fuel filter?? If so, lose it...

 

[jonmasaya]

What jets and which notch on the needle did you use?

I used the 130 jets in the kit. Clip is on the 4th notch from the top with two washers below it. Was considering lowering the needle...

 

[jonmasaya]

Make sure the fuel tank vents are working

Not sure. Is there a way of checking them?

Also, not using any inline filters.

 

[gearhead13]

If you run it again and it dies, pull the gas cap and listen for a sucking sound when you open it.
Did you install tha main air jet correctors that are in the kit? the little brass ones that you are supposed to glue in?

 

[Guest]

I used the 130 jets in the kit. Clip is on the 4th notch from the top with two washers below it. Was considering lowering the needle...

You want to lean it?
Why the washers under the clip? That doesn't do anything.

 

[jonmasaya]

If you run it again and it dies, pull the gas cap and listen for a sucking sound when you open it.
Did you install tha main air jet correctors that are in the kit? the little brass ones that you are supposed to glue in?

Pretty sure I'm getting a good flow through the gas cap nothing looks worn or damaged, but I will try and check it again.

I definitely installed the brass air restrictors.

You want to lean it?
Why the washers under the clip? That doesn't do anything.

I'm just copying the diagram in the DynoJet instructions. Seen here. The washers keep the needle a little higher I believe.

Troubleshooting guide for the kit also suggests lowering the needle if you get performance issues at higher RPMs.

 

[gearhead13]

Pretty sure I'm getting a good flow through the gas cap nothing looks worn or damaged, but I will try and check it again.
I definitely installed the brass air restrictors.
I'm just copying the diagram in the DynoJet instructions. Seen here. The washers keep the needle a little higher I believe.

Troubleshooting guide for the kit also suggests lowering the needle if you get performance issues at higher RPMs.

Right, one washer (usually bigger) goes below the clip for the spring to puch up evenly, but only washers above the clip make any difference in the needle position. The kit comes with washers so you can add a washer above the clip to lower the needle 1/2 notch.

2. Install the Dynojet needles on groove #4, using all stock spacers. Install the​

Dynojet washers above the E-clip.

 

[jonmasaya]

Ah ok, well I think I did that. I just copied the picture. Haha. I also get confused with what's "above" and "below". Regardless, I doubt a millimeter change in the needle height is causing my problems. It's definitely a major fuel starvation issue.

 

[79FiveFifty]

why are you crazies up in WA state trying to ride motorcycles in the winter with ice on the roads...

it's the altitude not the fuel problem, I mean you being dizzy and thinking riding on ice is ok!

Be safe

 

[gearhead13]

I live just across the water from washington state and it was 8C and sunny here today, saw several motorcycles on the highway

 

[jonmasaya]

I dunno about you guys, but I love riding on these cold, crisp days. Air is fresh and we have spectacular views of the mountains here in Seattle.

Sure as hell beats riding in the rain.

 

[Steve]

If your petcock is flowing enough on PRI to keep the bike running, it should be obvious that the petcock is not limiting your fuel flow. :-k

My opinion? (Well, you asked.) Back off the throttle just a little. With your pods, there is not enough vacuum to keep the petcock open at wide open throttle. Back off to about 3/4 throttle to see if that helps.

Not sure if you might have a small leak in the petcock diaphragm (that would show up as fouled plugs in #2 cylinder), but just about any vacuum-operated petcock you put in there will do the same thing. If backing off the throttle a bit does not help, you will have to change to a manually-operated petcock. (Did I hear somebody say "Pingel"? )

.

 

[Guest]

Ah ok, well I think I did that. I just copied the picture. Haha. I also get confused with what's "above" and "below". Regardless, I doubt a millimeter change in the needle height is causing my problems. It's definitely a major fuel starvation issue.

Believe it or not it probably does make a difference.

 

[jonmasaya]

If your petcock is flowing enough on PRI to keep the bike running, it should be obvious that the petcock is not limiting your fuel flow. :-k

My opinion? (Well, you asked.) Back off the throttle just a little. With your pods, there is not enough vacuum to keep the petcock open at wide open throttle. Back off to about 3/4 throttle to see if that helps.

Not sure if you might have a small leak in the petcock diaphragm (that would show up as fouled plugs in #2 cylinder), but just about any vacuum-operated petcock you put in there will do the same thing. If backing off the throttle a bit does not help, you will have to change to a manually-operated petcock. (Did I hear somebody say "Pingel"? )

.

Hmmm. Well, it definitely ran worse on PRI, it was just the only option to get home without pulling over every few miles. The issue only comes up at 60mph+. I never had the throttle pulled all the way back... Not sure how to explain this, but I could kind of find a sweet spot. Too much throttle and you get a resonant sound and no power.

I should also mention that the switch on my petcock is ridiculously hard to move, often requiring a wrench. I'm thinking its time has come either way. Is the non-vacuum petcock really the way to go? I've ridden hondas for a while and I always forget that damn thing. ("WTF! I can't be out of gas already!")

 

[Steve]

When you installed your Dynojet kit, did you also drill the slides?

DJ includes a drill to enlarge the vacuum port on the bottom of the slides to enhance operation with limited vacuum.
If you have not yet drilled the slides, that might be (at least part of) your problem.

.

 

[jonmasaya]

When you installed your Dynojet kit, did you also drill the slides?

DJ includes a drill to enlarge the vacuum port on the bottom of the slides to enhance operation with limited vacuum.
If you have not yet drilled the slides, that might be (at least part of) your problem.

.

Yup! Drilling those out was the scariest part.
I followed those instructions to a T.