Daycruiser motor help

[Kurtis500]

Just bought a v-drive daycruiser and took it out for the weekend. Everything ran outstanding and we put at least 80 miles on the boat. The one and only problem I am having is a stumble when getting off an idle. The motor runs strong at all ranges, it just stumbles after the velvet drive is shifted into gear and the accelerator is slightly moved forward. I just pump the throttle once up and back then up again and it takes off great. I would rather not have to do this. The motor is a recently rebuilt BBC mildly hopped-up. A new MSD distributor, 6al box and blaster 2 coil. Also has a new double pumper Demon carb on it. I timed it at 32 degrees.
I havent yet looked into it closely, and just thought I would see if anyone here has ran into the same problem before...maybe it would narrow my search. I'm suspecting the problem is somewhere in the accelerator pump set-up. Although it works just fine, it may be too much or too little. Also, is there some vacuum type connection between the velvet drive and the motor? I've built a few motors along with my race motors myself and havent encountered this problem since they are set-up from the start. But since I dont know whats in the motor its going to be a little of a guessing game till I get it figured out.

[spectras only]

Kurtis , if you have your Demon's primary bowl towards the stern [v-drive setups are diff from jets], I would install the jet extensions [available at any speedshop that sells holley carbs] and make sure you have 30cc primary ,50cc acc pump on the secondary bowl.I think the demon carbs are the same as holleys other than the bowl shape .Demon's bowls were exactly the same as holleys originally and they had to change them to avoid lawsuits ,I think.

[Kurtis500]

I had thought of that, but the carbs are full to the levels with fuel. They have a sight glass on the side and stay up even when it stumbles. :confused: It does this on the slightest or hardest acceleration.

[Rexone]

Sounds like an accelerator pump issue to me. Is the primary acc pump squirting properly?

[Maxey]

Kurtis,
What size Demon do you have? If it is an 850, make sure that it has annular boosters. If not, send it to Demon and they will change them for you at a reasonable price. The demon carbs flow high numbers. A 750 might be a better application for your engine/appication. I experienced what you are going
through. Hope this info helps.
Maxey

[GofastRacer]

Got to agree with Rexone, check accelerator pumps, may need to go up one size!.

[Kurtis500]

Will check those. I believe they are the 30cc pumps.
What still seems to confuse me is that I can shift it into gear and just tap the throttle forward a little. It will then stumble unless I accelerate above the rpm range that is just above the idle.
Is there any kind of link between the velvet drive and the motor at all?

[Terminal Velocity]

Check out this at Holley. May be a Demon but the principal is the same...
http://www.holley.com/HiOctn/TechServ/TechInfo/TI-221.html
Sounds to me like maybe a change in the squirter may be in order.

[SK48]

Rex and Gofast are on the right track. I have a Hallett v-drive cruiser with a 850 Holley. We tuned it on a dyno etc. but in the boat it would stumble a little on take off. I just started increasing the accellerator pump nozzles a couple of sizes at a time. With a lot of early morning river time and a pad of paper I got the boat to leave from a dead start without a problem.

[Kurtis500]

I have noticed a delay in the accelerator pump when the throttle is touched. This is where I suspected the problem is, though I havent looked into it yet. Will look at that first on Thursday when we take it out.
Always pays to ask first. Thanks SK48, I figured others had the same problem with the same set-up before.

[GofastRacer]

Curtis, the numbers on the squirters are the sizes of the holes in thousands, get yourself a #61 to #80 pin drill set and take it with you to the lake, drill the holes out .002(no more) at a time until the stumble goes away. Stock carbs usually come with too small squirters to begin with. This is a common thing and very easy to fix!.. :)
Another thing to check, make sure that the pump actuates as the throttle is opened, if it don't, you will have a stumble!...
[ June 17, 2003, 07:43 PM: Message edited by: GofastRacer ]

[Kurtis500]

Gofast, I've got a whole asortment of HP accelerator pump nozzles for my other boat. I havent looked into the Demon yet, but I may try these if they fit. I know they are pretty big, I used them on my blower motor before I switched to injection.
What I recall about the carb was the squirt came later after the throttle was already partially opened.

[GofastRacer]

Kurtis500:
What I recall about the carb was the squirt came later after the throttle was already partially opened. No, if the squirt came later you would have a gulp of air without fuel, that's where you would get a stumble, you have to give it fuel along with the air. If you want, e-mail me your number, I'll call ya!..

[Kurtis500]

Yep. thats what I'm going to change first. I never looked into the problem at the lake and havent lifted a finger. I could have worked on it before i asked, but this helps narrow the search A LOT! First thing I am/was going to do is adjust the acelerator pump timing and nozzle size. This should solve it.. hopefully :p Since I didnt build this one myself I cant guage the proper carb for the motor. I never have liked doing things backwards, but after driving this thing for many miles already, I'm more than happy to get it fixed any way that is needed.
[ June 17, 2003, 08:24 PM: Message edited by: Kurtis500 ]

[Itsahobby]

I am no expert, but were there new gas lines
installed? My boat did the same thing. Turned out
I had rubber grit in the bowls that got into
the check valve.
ItsaHobby