Need some carb help!

[dano214]

Hello everyone,

Heres the run down of what i have going on, I have a 2001 GTI with a 720 and a single 40i-38 carb. I just rebuilt the motor and carb, put it all together fired it up and it idles fine but as soon as i would tap the gas it would die. After some investigating i found that the accelerator pump was not working. There was so much crap in there it was not repairable. So I looked in to replacing it but they want over 200 dollars for it I talked with a mechanic at a local shop to see if i can just rejet and not use the accelerator pump, we looked it up and a 97 GTI is the last year of the non accel pump carb and its a 40i-38 also. So i rejeted to those specs boat runs good but im stuck on something, if i gradually increase the throttle it pulls rpms fine but if i go from idle to full wide open it bogs and will even die? I thought i knew what i was doing but im pretty much lost at this time. :banghead:

specs
pilot jet- 70
main jet- 175
n/s- 1.5 with silver spring
lsa- 1 turn
hsa- 1.5 turn

 

[Dr Honda]

That jetting should work. But I do see one thing. You say 'N/S 1.5 with silver spring"... did you actually check the pop-off? It's hard enough to get them to run without the accel pump (that's why they added them) but what you are describing is a pop-off that is extremely high. I'd set it kind of low. Probably around 25 psi to help get you past the transition.


Also... did you do the rebuild with OEM Mikuni parts? (after market parts suck)

Finally... Do you have a stock air box on it?

 

[riding high]

Box it up and send it to Doc to get it rebuilt. A wise investment!!!atriot:

 

[dano214]

Hey Dr Honda,
The pop off if i remember correctly was at about 32-33 is that to high? I was thinking thats were it needed to be. I rebuilt it with genuine mikuni parts, even the jets. I am running the stock air box.

 

[dano214]

The question of the day, if it bogs when I hit the throttle does that mean its running to rich or lean?

 

[Dr Honda]

Sorry I missed the last post.

32 should be OK on a 1.5... but like I was saying... without the pump... you need to massage it a little. If it was me... I would drop it down to about 25.


If you hit the throttle, and it bogs... that's a lean condition. If it was stuttering (like a miss) that's rich.


Ummmmmm.............................................



I'd pull the carbs, lower the pop-off, and put in a 72.5 pilot. That should help clear it up.

BUT.... do you have a factory airbox on the ski????

 

[dano214]

Hey Doc,
Im pulling my hair out! :banghead: So i messed with the carb, my pop off was at 34 so i dropped it to 25 but it still doing the samething, so i thought well lets see what she'll do if i drop it to 18? still the same. Im so lost right now, i don't know if i should just drop the cash and buy another carb with a accel pump? im all ears doc..... :bigear:

And yes i am running the stock air box.

 

[Dr Honda]

Did you put in the bigger pilot jet?

 

[dano214]

Paging Dr. Honda.......

Hey Doc, I got the pop off set at 21psi and i up the pilot to 72.5. The ski runs great on the trailer but when i put the ski in the water it still bogs on acceleration, if i pump the throttle and get it past the bog it runs great. Its also alittle hard to start when i first get it in the water or after it sits. The plugs look like its running rich on bottom end but look nicely brown on top end. Im still breaking this motor in and have added oil the fuel during break in, would this cause any of these problems?

 

[Dr Honda]

To transition a 40mm carb without the pump... you may need to go up to a 75 or 77.5 pilot.

Did you verify that all the transition ports are clear?