Blaster Fuel issues with B1 1200 swap

[DAG]

Swaped in a GP1200 into the B1 and it runs perfect. The only issue I have is when I cut it off, never seems to want to start back up (easily). I pulled the carbs and rebuilt them and it did not fix the issue. The ski does not have the problem on land. And typically on water if i let it idle to a stop its also not an issue. To me it seems to be loading up for some reason? I though maybe a leaky N/S but they are good and popoff on all 3 carbs are perfect. I'm not running a oneway on the tank vent just the stock white water catcher thing. It seems when the motor gets warm or the tank displaces fuel the issues comes on. Thoughts? Anyone else having this issue with a 1200 swap?

 

[JT_Freeride]

It's gotta be the one way valve. You need to have tank pressure

 

[DAG]

The stock B1 tank does not have a 1 way valve... why would swapping in a 1200 make any difference? If anything I think a overpressured tank would be the culprit not the solution. I might add the ski will not start if prime fuel into it. But will start after being on the battery for 30 seconds

 

[tom21]

what needle and seat, spring and popoff are you running?

 

[BMWtech]

The stock B1 tank does not have a 1 way valve... why would swapping in a 1200 make any difference? If anything I think a overpressured tank would be the culprit not the solution. I might add the ski will not start if prime fuel into it. But will start after being on the battery for 30 seconds

My stock tank has a 1 way valve on it.

 

[Byeai]

Blasters have one ways on tank from factory

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[DAG]

I'll add a oneway and try again. Thanks guys

 

[Squid121]

It's gotta be the one way valve. You need to have tank pressure

How does the one way valve add pressure to the tank?? The sole purpose of that valve is to prevent gas from spilling back into the hull and to allow air into the tank to replace the fuel that is being used. That's the purpose of that entire line coming off the tank with the "one way" or check valve as Yamaha calls it, the water separator, and the air vents by the back of engine where the hood latches.

As for the original question, make sure that vent line is not kinked or blocked in any way. Or simply remove it and see if the condition persists. But I would always run a check valve on the tank. Good luck

 

[DangerBoy]

How does the one way valve add pressure to the tank?? The sole purpose of that valve is to prevent gas from spilling back into the hull and to allow air into the tank to replace the fuel that is being used. That's the purpose of that entire line coming off the tank with the "one way" or check valve as Yamaha calls it, the water separator, and the air vents by the back of engine where the hood latches.

As for the original question, make sure that vent line is not kinked or blocked in any way. Or simply remove it and see if the condition persists. But I would always run a check valve on the tank. Good luck

They dont "add " pressure but the fuel pump return line does. the check valve keeps that pressure in the tank

However ,I never tune skis to need a pressured tank to run , and I usually disable or eliminate the one way valves , I do run one way check valves on my pick up lines

 

[Squid121]

They dont "add " pressure but the fuel pump return line does. the check valve keeps that pressure in the tank

How does the return line add pressure? The fuel pumps pump X amount of fuel from the tank at all times, the carbs then use a certain amount of that fuel, the remainder of which is returned to the tank. Therefore, the fuel returning to the tank via the return line is less than that which was drawn out to feed the carbs. So the fuel return line does not pressurize the tank. My previous statement is accurate about the check valve allowing air to enter the tank to replace the fuel used and to keep fuel from spilling into the hull.

If a ski will only run or run better by the fuel tank being pressurized, then the carbs need attention because they are not doing their job correctly.

 

[DAG]

If a ski will only run or run better by the fuel tank being pressurized, then the carbs need attention because they are not doing their job correctly.

I agree with this. I don't see how adding a check valve will help the issue I'm having. Especially since I rebuilt the carbs. I'm down to learn something new. I'll report back how adding the oneway effects the performance.

 

[mike b]

The stock B1 tank does not have a 1 way valve... why would swapping in a 1200 make any difference? If anything I think a overpressured tank would be the culprit not the solution. I might add the ski will not start if prime fuel into it. But will start after being on the battery for 30 seconds

Have the same swap with my 96 and the tank i have has a one way valve. IF thats all that is different between the gp and blaster hull that would be what i think the problem would be. Also, have you tuned the carbs. I was told by either 701Dave or somebody else on this site who has done many of these that the stock carbs need to be leaned out about 1/4 on the low speed. Don't know if that helps but thought id pass my knowledge along

 

[tshank123]

How does the return line add pressure? The fuel pumps pump X amount of fuel from the tank at all times, the carbs then use a certain amount of that fuel, the remainder of which is returned to the tank. Therefore, the fuel returning to the tank via the return line is less than that which was drawn out to feed the carbs. So the fuel return line does not pressurize the tank. My previous statement is accurate about the check valve allowing air to enter the tank to replace the fuel used and to keep fuel from spilling into the hull.

If a ski will only run or run better by the fuel tank being pressurized, then the carbs need attention because they are not doing their job correctly.

The pressure comes from the fuel itself. Its like a fuel jug that you leave out in the sun, it blows up like a balloon. If the one way valve is good, and there are no other leaks in the fuel system, it should hold pressure. You should be able to blow through the one way valve and watch your tank expand like a balloon. If you open the cap, you should hear the pressure relieve.

To the original question, did you replace the check valves in the fuel pumps when you did the carb rebuilds (the little clear disks)? The 1200s are notorious for buckling those, its a very common problem.

 

[DAG]

Out of the 6 disk only one of them had debris under them which was bent & needed replaced. (those things frucking suck to replace) Kind of off topic but anyone have tips to get the rubber nipple pushed back through the metal separator plate? Took me maybe 15-20 minutes with it lubed up real good. Otherwise I would have replaced the ones that looked ok just to make sure they did not get to flimsy?

 

[Twinturbostang]

Do you have a jet in the return?
do you have the primer in the feed?

 

[DangerBoy]

Out of the 6 disk only one of them had debris under them which was bent & needed replaced. (those things frucking suck to replace) Kind of off topic but anyone have tips to get the rubber nipple pushed back through the metal separator plate? Took me maybe 15-20 minutes with it lubed up real good. Otherwise I would have replaced the ones that looked ok just to make sure they did not get to flimsy?

Make a tool like this

 

[glennbbautomachine]

Out of the 6 disk only one of them had debris under them which was bent & needed replaced. (those things frucking suck to replace) Kind of off topic but anyone have tips to get the rubber nipple pushed back through the metal separator plate? Took me maybe 15-20 minutes with it lubed up real good. Otherwise I would have replaced the ones that looked ok just to make sure they did not get to flimsy?

Make the tool that Mikuni suggests in there carb rebuild kits, its a time and finger saver!

 

[tshank123]

Do you have a jet in the return?
do you have the primer in the feed?

I know you're not suggesting a primer on the feed.

The jet in the return line is for the updated carbs. If the returns inside the body of the carbs have been opened up, you need the return line restricter. I dont think that causes this problem but it will give you some tuning problems.

 

[air blair]

Check valve for sure.

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[DAG]

Ahh, sweet tool, first I've seen that. Thanks! Plunger style primer T'd into the reserve pickup just before the fuel selector. OEM carbs nothing done to them. I do not have a jet in the return. The return line does have a pretty good flow rate but probably due to comparing triple vs. twin carbs.