Topic: Accelerator pump driving me crazy.

[lucky]

Foggy-headed morning project....
12" x 3/16"  brass tubing was $2 at local hobby store.
3@ .350"
3@ .450"

Most important....Was the inside diameter 1/8 inch???

If not that hobby shop tubing is made in such a way that the next size down will slip inside if the next larger tube and so on.

[Tugboat]

Waiting to see if this works!! I threw away my restrictors (unbeknownst to me) when I rebuilt my carbs.

[TwoTired]

I know from personal experience the #42 idle jet will fix the problem. I tried a #40  and it still did not work good enough. 

...And, I STILL don't believe your accelerator pump was working as it should.  ...And you "fixed" the wrong thing as a band aid, without observing the true negative effects.

I don't understand why you wish to propagate this mistake to others.  But, if they don't care, all I can do is point out the obvious.

[lucky]

Waiting to see if this works!! I threw away my restrictors (unbeknownst to me) when I rebuilt my carbs.

If you threw the restrictor away I would add them back in.
I had mine off by mistake and when I added them back on it did seem to work better.
Anyway they did not solve the problem below 1/4 throttle.
I still went to a #42 idle jet before it worked right.
The only thing I have not done with my 78 carbs is to change the needles to adjustable types and go down that road.
I bought some 1976 needles which measured the same, but now I put my 1969 carbs on and never looked back.

[lucky]

I know from personal experience the #42 idle jet will fix the problem. I tried a #40  and it still did not work good enough. 

...And, I STILL don't believe your accelerator pump was working as it should.  ...And you "fixed" the wrong thing as a band aid, without observing the true negative effects.

I don't understand why you wish to propagate this mistake to others.  But, if they don't care, all I can do is point out the obvious.

TWO TIRED ....I am trying to not get into a personal dialogue with you.
I just write my ideas, and I listen to yours.

Let our personal experiences guide us.

You never want to change idle jets.
I will change idle jets if it gets good results.
That is where we do not agree.

I did do EVERYTHING correctly to my carbs and accelerator pump system.
I even bought a brand NEW accelerator pump bottom plate complete.
I put in the restrictor tubes when I found out about them.
I spent lots of money on my 1978 carbs. I still do not like them.


IF I had the money, I would by the CR carbs. End of story.
Right now I have the poor mans version of CR's the 1969 carbs.

[Ira]

With respect to the passionate disagreement here, I'm going to spend the next few days doing some riding around town and feeling things out.   

Some people say it does not hesitate or bog but they baby the throttle to get the response to be smooth by rolling on the throttle slowly.

This was definitely the case before I enlarged the "ear" passages on my pump.  It is certainly less-so now, so fixing the pump made a significant difference for my bike.

When I set up a motorcycle I expect NO hesitation at all at any time.

However, I would not say this describes my bike right now.  There is hesitation at 1/8 - 1/4 throttle, but much less than before.  I'm willing to risk $20 on idle jets to see if it makes a difference.

...And, I STILL don't believe your accelerator pump was working as it should.  ...And you "fixed" the wrong thing as a band aid, without observing the true negative effects.

Pardon my ignorance, but what negative effects would it have if I used a #42 instead of a #35?  What should I be thinking about before I do something like this?

[TwoTired]

...And, I STILL don't believe your accelerator pump was working as it should.  ...And you "fixed" the wrong thing as a band aid, without observing the true negative effects.

Pardon my ignorance, but what negative effects would it have if I used a #42 instead of a #35?  What should I be thinking about before I do something like this?

Uses more gas, which (besides being wasteful) helps to "wash" the oil off the cylinder walls, leading to faster ring, cylinder, and piston wear, puts more deposits on the spark plugs while idling, and helps everyone put more hydrocarbons into their lungs.

With my pump issues, I had to go three rounds with the diaphragm "Mouse ears".  First pass was with the standard cleaning of the carbs and check ball function, without knowing about the "Mouse ears" or what they should look like.  I was just happy the diaphragm wasn't cracked.  Second pass, in response to awful hesitation, I enlarged the hole (was pinhole).  The bike responded much better to throttle twist.  Still had some hesitation.  On the third pass, I enlarged the hole to be a slightly larger size than the casting holes.  That's when all the hesitation went away with throttle twist.  Realize that when the lower pump body is put on, the screws squish and extrude the rubber to swell a bit into those holes.  That's why I made them a bit oversize in the rubber "ears" while still ensuring they seal properly.

Cheers,

I did not give up and switch to "sloppier" carbs.  As I knew the bike wouldn't behave badly if everything was working as it should.

[Ira]

It's been a while, but I've made progress.  Rather that go up an idle jet size, I adjusted my mixture screws out to three turns.  The hesitation is nearly gone and the power feels good throughout the rpm range.  I've been experimenting with different settings over the last couple weeks and this seems like the best.

[flybox1]

Foggy-headed morning project....
12" x 3/16"  brass tubing was $2 at local hobby store.
3@ .350"
3@ .450"

Most important....Was the inside diameter 1/8 inch???

If not that hobby shop tubing is made in such a way that the next size down will slip inside if the next larger tube and so on.

Yes. The ID was 1/8, and worked perfectly. All Carbs squirt equally, and forcefully. My #4 had a soft squirt, and this mod fixed it properly. All squirt the same.

[lucky]

But if you have a 4 into 1 exhaust  it still may not help the hesitation problem even with a stock air filter box and filter.
Put in #42 mm idle jets and set the mixture screws to 3/4 turn. Main jets #120.

Quick question about this.  I re-read the '81 Motorcyclist magazine article about jetting for a 4-1.  This is what they recommend:

Jetting for either of these pipes is rather easy. Simply install the K&N stock replacement filter, change the pilot (idle) jets to No. 35s, go up two sizes on the main jets and adjust the pilot-air screws out one to one and one-eighth turns. Be sure to synchronize the carbs.

What is "two sizes up" on the mains?

My carbs are jetted w/ #120 main and # 35 idle, pilot at 1 1/2 turns.

This is what the squirt from the pump looks like on each carb.  Sorry for the bad lighting and shaky video, I was holding a flashlight and my phone at the same time.

The #35 idle jet is NOT going to work. It will hesitate badly.

[Ira]

I'll order the #42 jets as soon as Sirius has them back in stock, which is 3-4 weeks from now.  Until then, adjusting the mixture is the best I can do.

[lucky]

if all 4 of them squirt like that, you should be ok.
mine squirt a little more forcefully. i went with the smallest ID clear fuel line i could get on the 'between-bowl" connectors to up the pressure out of the squirters.  this might have helped.
Tonight i will road test my setup for my 4 into 1's(minimal baffle) after a vacuum sync.
35/120 jets.  stock airbox.  fuel mix screw at 1.5 turns out.
i'll keep you posted on how that goes.

Rubber fuel hoses between cabs on those models have two brass restrictor tubes inside the rubber fuel hose that raise the pressure. The inside diameter of the brass tubes is 1/8 inch.

[lucky]

Foggy-headed morning project....
12" x 3/16"  brass tubing was $2 at local hobby store.
3@ .350"
3@ .450"

Looks good Flybox1!

Most important....Was the inside diameter 1/8 inch???

If not that hobby shop tubing is made in such a way that the next size down will slip inside if the next larger tube and so on.

Yes. The ID was 1/8, and worked perfectly. All Carbs squirt equally, and forcefully. My #4 had a soft squirt, and this mod fixed it properly. All squirt the same.

[bollingball]

I'll order the #42 jets as soon as Sirius has them back in stock, which is 3-4 weeks from now.  Until then, adjusting the mixture is the best I can do.

Buy a couple of extra sets of plugs while you are at it. If you think that is the fix why wait just ream out the 35s That would not screw it up any more than the 42s Either way get the plugs for when they foul out. My 78 runs just fine stock carbs But they are set up correctly. I went through most of the same problems as TT and listened to all of luckys nonsense. The last thing I did that really made the difference was getting the fast idle cam and pump rod setup properly buy the book but a little tight on the pump rod gap. Bottom line if your parts are in spec and you set them up buy the book they are very nice carbs and work just fine period.
Ken

[Ira]

Honestly, I don't know who to trust on this one, so I'm trying any advice as long as it's reversible.  In other words, not reaming out the #35s .  The #42 jets are $20 for a set, so if they don't do anything for me, not a big loss. 

My setup isn't stock- I have the Kerker 4-1 and K&N air filter.  However, fixing my accelerator pump made a HUGE difference in the way the bike runs.  Fiddling with the mixture screws has further improved the situation. 

[bollingball]

Honestly, I don't know who to trust on this one, so I'm trying any advice as long as it's reversible.  In other words, not reaming out the #35s .  The #42 jets are $20 for a set, so if they don't do anything for me, not a big loss. 

My setup isn't stock- I have the Kerker 4-1 and K&N air filter.  However, fixing my accelerator pump made a HUGE difference in the way the bike runs.  Fiddling with the mixture screws has further improved the situation.

I guess the title to your posts is not correct. I see now you say your accelerator pump is working that is good

[flybox1]

My #35's cause no hesitation at all during hard acceleration.

I have my restrictor tubes between my Carbs, and my accel pump squirts fuel as it should.
I have a 4-1 kerker with a tiny baffle. My fuel mixture screws are out 7/6ths turns.  Two .5mm shims on each of my slides. My float height is set at 'top of the press in idle jet".  I have a stock airbox and filter.
#120 mains, and my plugs are all tan.
I have no more popping at idle. Only a popping/burble on decel.
I will remove .5mm on the shims and see if that helps to tune out the popping...

[fivestring]

Here's some pictures I took while salvaging the brass inserts in my old tubes.  Had I not read this thread, I would have tossed them.

The two slightly longer inserts came from the center tube.

[harisuluv]

I know this is an old post but I was looking at the pictures posted right above and the ID definitely did not look like 1/8".  The tubing looks like it is a much thicker wall also than 1/16".

I did an autopsy on one myself and took some measurements and found that the tube is as follows.

ID:              2mm
OD:             4mm
Length:        9.50mm (two outer tubes, didn't measure the center one.)

[lucky]

I have a kerker 4-1 and stock airbox with a k&n filter.  I recall an old article someone posted about that specific setup, which I'll need to reread and make sure my jetting is right. 

I read the chopper forum tutorial on cleaning the check ball. I was hoping that since i could spray fluid through the valves with a straw, they were ok, but i guess i'll take the valve out of the bottom plate and see what it looks like. 

The rubber hoses are stock and even have the little wire clamps on them.

I'd like to avoid purchasing new carbs, but I appreciate the advice.  If I can't figure this out I'll go that route.

You do not have to buy new carbs.

[lucky]

I realize that before I said none of the accel pump jets were squirting.  I don't know if I just couldn't see the squirts before (without a light) or if the carbs are behaving differently today for some reason.  I haven't touched them since the first time I posted in this thread.

Either way, does my video look like the correct behavior, or should they be squirting more fuel?

I could not view your video as it was marked only for private use. You need to go bck to You Tube Video manager and change the setting to PUBLIC.