93 Yammy V4 - 115hp - big flat spot from idle to full throttle

[scottfromoz]

Hi all. Perhaps a product of not enough use over several months..read no use over about 3 months I took out the old girl the other day. There was nothing - just starvation it seems between idle and pretty much flat out (or very close to it). As I opened the throttle from idle it felt like it was starving and if I kept opening to 2/3rds it would just snuff out. The only way to get her onto the plane was to tickle the choke a bit from the control box with the throttle 3/4 open to induce some more petrol and then suddenly she would take off like a scalded cat...once on 3/4 to full throttle she was fine. I dont know if these carbs have a acceleration plunger to squirt more petrol in...and if so whether in any case both carbs would be blocked...Im thinking blocked from sitting for so long, but why both?

Any help appreciated.

Cheers

 

[ianyoung77]

Re: 93 Yammy V4 - 115hp - big flat spot from idle to full throttle

Hey Scott,

This seems a really common problem and you are right about the fuel. I would guess you have crud in the fuel so you have to remove crud and then clean out the system. The first place to look is the fuel filter. Does it have anything in it?

 

[scottfromoz]

Re: 93 Yammy V4 - 115hp - big flat spot from idle to full throttle

Thanks matey. I havent got any water in the separator (big arse one) but I suspect that the fuel has dried out in the bowls and left flaky crud behind and its found its way into the idle or accelerator jets - dont know anything about the internals of the yamm carb though.

Cheers

 

[ianyoung77]

Re: 93 Yammy V4 - 115hp - big flat spot from idle to full throttle

That model should also have a fuel filter in the motor. Assuming your separator is working properly the filter should be clean but it doesn't hurt to look. There are a couple of o-rings which you need to look out for but generally you can reuse them.
I think you are probably right that the carbies will need cleaning but I don't think not using the motor for 3 months would cause crud to form. It's possible the crud is elsewhere and you will get the boat running beautifully for about a month before having to clean it again. I would fully check the fuel system before cleaning the carbs. Empty the tank and check it closely. Check all fuel connectors are perfect. Change the cartridge on the fuel separator, check the filter. If you have never changed the fuel pump then change it. You can overhaul it but it's not really that economic. Even if you replace it have a look in the petrol side to see if there is any residue.
Once you've done all that the carby cleaning is easy but you will need to synch and adjust afterwards.