Cornering hard, fuel starvation?

[shenders]

Well I guess I’m way off base here. The pump does look like the old type (omc) pump. I would
hook it up like your manual shows. Float level and the baffles I guess is your next place to ck.
Not sure how your going to get more fuel pressure or flow. The pump is only going to pump
so much.

[Ron Hill]

We never disconnected the OMC pumps, we just added a Holly between the tank and the fuel pumps. The Holly just "OVER RODE" the OMC pumps, and we ran low enough pressure that they basically worked like "Floatless" carbs. I know our 235's would die in the corner without a Holly pump!

Tim Soares actually plumbed the line around the pump, so if the pump quit the omc pumps could still suck the fuel around the pumps. OLD Enduro racers knew finishing was half of winning.

I just put in a call for Tim to see if he remembers what pressure we set the props!

[whiplash]

we run a holly blue top at between 3.5psi and 4.5psi on our tunnel with a omc115 as we had the same issues in the corners and at the end of the straights. The other thing you can do is fill the top of the carb with a layer of epoxy reisin to stop the slosh around the air vents.

[Yellowjacket]

Is it starving or flooding??? If you don't know you can run it into the corner and as it dies hit the enrichment device. If it picks back up, it's starving, if it's flooding it will get worse.

Some carbs just aren't built for high lateral g loads and these floats may be just not designed for what you are doing. You also want to make sure the floats aren't sticking or binding when the lateral load is applied. Depends on how the floats are swinging in the bowl and where the float is relative to the jets.

At this point it may be a lot easier to replace the carbs than fooling around and trying to get something that works. Look as weather or not the g loads are causing the float to cut off fuel (heigth of the fuel in the float bowl relative to the main jet), or flood (fuel level is dropping at the float relative to the jet) and go from there. I doubt that it's as much a fuel pressure thing as it is a float level relative to the jet problem and that might not be solvable.

[Per]

Thanks everybody!!

Mike Schmidt:
I would really love to put a set of Mikuni carbs on that engine! I have already found what I think would be a good candidate for the swap, carbs from Yamaha RD 350LC should be perfect.
Fitting them to the engine and jetting them correctly would on the other hand take ages for me since work / family takes most of my time right now

The fuel pickups in the tanks will be changed to next summer and I will bear in mind what you wrote about it!
I will keep you posted, the result will show first in a couple of month though, the lake here is more suited to ice skates right now

shenders:
I was thinking maybe adding another vacuum operated pump on the top crank case would help. Maybe I'm wrong here but plumbing in a pump in series should raise the pressure if the "resistance" from the carbs are the same. If plumbed in in parallell the two pumps should together have a larger capacity
Than again, reading Yellowfjacket's post made me really think...

Ron:
Perfect! If dual vacuum operated pumps won't work I now were to find a really cheap electric one that probably have the roughly the right pressure for the task. Soo true what you wrote about winning, in our first and so far only race we only made it halfways...

Whiplash:
I'll take a look at the top portion of the float bowl and see if there is any place that the fuel might escape, good info about the pressure levels!

Yellowjacket:
You raised a few very interesting question! I have assumed that the engine died from fuel starvation since that is what have happend to me before
It could of course be flooding aswell but my gut feeling says starving, right now I feel a bit stupid for not making such an easy check...
The float is guided by a vertical shaft, maybe the lateral forces make it stick a bit...
After your post there is several things I need to check.
The carbs might not be built for this kind of use but I seems to remember that the Crescent CS 500 engine used the same type, maybe I should talk to some of the guys running those engines on the classic cabover hydros....
Changing carbs will however be a last resort and if nothing helps I can always put an OMC 56CI triple on the boat, probably a lot less hassle

//Per
PS: English is not my native language, excuse my spelling and grammar...

[Yellowjacket]

In looking at the outside of the float bowls I was thinking that the floats were probably not swinging, but were a guided on a rod type deal. Those type of rigs are much more prone to sticking than swinging floats.

If it's starving from sticking, then the float is sticking in the top position. Hard to think that they would stick with oil in the fuel but some designs suck. You might try some more fuel pressure and that may help, but I doubt it. A very light spring on the top of the float also might help but it's going to have to be really light not to screw things up.

What is likely happening is that the fuel in the float chamber is climbing the wall and the float has a lot of extra bouyancy and, even though the bowl level is getting lower, the jet is starving since the distance the fuel has to get pulled up is higher and there isn't enough suction to do that. If that's the case, then adding a spring (again, a really soft one) on top of the float might help reduce the extra bouyancy and get you where you need to be.

Lastly, if you really are starving, adjusting the float to the highest level allowed, or a bit more may help too, since that opens the needle sooner and doesn't starve as soon.

[shenders]

I think at this point, if it was me I would raise the float level 1/16 “ just to see what would
happen. Gotta do something, can’t just keep talking about the problem.

[Per]

shenders:
I will have to make you disapointed, we have 8" of snow and roughly the same amount of ice on the lake
In about two month the snow and ice is hopefully gone and testing season begins.
Right now it is only planning and some work shop time, but I think it is better to ask questions in the winter time when people have time to discuss
I have alot of good suggestions from all of you guys, some of them will certainly be incorporated in the rebuild of the blown engine!
I will let you now how things turn out

Once again, thanks for all good suggestions!

//Per

Short video from the first test last summer...
http://www.youtube.com/watch?v=tfrttFpzzTo