2000 Yamaha GP1200R- Fuel/Air Issue?

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I have 2000 GP1200 that has Riva modifications on it. The issue I'm having only occurs above 4500rpm. It starts fine using the added primer and runs and accelerates perfectly at lower rpm's. My issue is that at WOT it will cut out and re-catch around 4500-5000rpm. Last winter the carbs were completely rebuilt, the summer before I replaced the fuel petcock. It seems like it has issues getting fuel unless you select "reserve" over the "on" settings. I'm not sure if this has anything to do with it. I also cleaned the fuel/water separator as well as replaced an inline fuel filter. This ski has been modified quite a bit, but up until last year it never gave me any issues. I'm the second owner. It's a blast to ride and I want to solve this issue.

Where should I start?

 

[alldodge]

Maybe running out of fuel
Fuel pump, filter, fuel line restriction

 

[top-pop]

Yes I think it seems to be starving for fuel. Where's the fuel pump located?
The filter is brand new. Next I could check the lines and pull the tank. Is that very difficult ?

 

[alldodge]

Not familiar with Yams, but they all operate about the same

Blow the lines out with air but be careful with not to much air. Might be a screen in the tank or other. You have Mikuni carbs and pumps. The pump is a small rectangle mounted on the motor. It uses exhaust gases to work the pump. Pump is in the link below

https://www.powersportsid.com/2000-yamaha-waverunner-gp1200-fuel-pumps-components/

 

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I'll give that a try. Going to be a couple months before I can test it though. I'll write back then.

 

[QBhoy]

Hi. I think this is the non power valve 1200 more reliable version, going by the year. Not much to go wrong with these motors to be fair.
Id say your right in thinking it’s fuel related. I’ve never had the triple like yours, but had the twin 800r ski and got to know that very well with a rebuild and a few common issues.
I’d look towards the fuel pump on carbs. You mention there is a primer fitted. Far too often guys fit these to try and get around an under lying issues with something else. Like the pumps being worn or faulty and not able to pull fuel through initially on their own, without the help of a primer. The worse again they often fit a primer bulb from an outboard fuel tank that can rupture things with too much pressure.
Other thing to look at is the check valve on the line just immediately as it comes out the tank. They can cause issues. Also check your vent isn’t clogged too.
Also make sure your in line fuel filter is installed the right direction of flow. Very easy to get this the wrong way round and restrict the fuel.

 

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Those are all great suggestions. I'm going through it this weekend. I hadn't thought about the vent. I'll double check the fuel filter too. It most def is starving for fuel only at the upper end. The primer was put on this ski many years ago along with Riva cylinder kegs, d-plate install, oil pump delete and Solas impeller by a previous owner. The fact that it only really runs on the reserve setting should be a clue to me but being that I've never had the tank out I'm not sure how the two pick ups work
.
Two questions..... Is it difficult to pull the whole tank? How hard is it to replace the fuel pump?

Thanks!

 

[QBhoy]

Those are all great suggestions. I'm going through it this weekend. I hadn't thought about the vent. I'll double check the fuel filter too. It most def is starving for fuel only at the upper end. The primer was put on this ski many years ago along with Riva cylinder kegs, d-plate install, oil pump delete and Solas impeller by a previous owner. The fact that it only really runs on the reserve setting should be a clue to me but being that I've never had the tank out I'm not sure how the two pick ups work
.
Two questions..... Is it difficult to pull the whole tank? How hard is it to replace the fuel pump?

Thanks!

The reserve is just a lower suction from the tank. I’d suggest you have a restriction in the main fuel line. As in a check valve getting blocked or similar. Check that fuel filter too.

 

[top-pop]

I pulled the fuel pick up today. The check valve was working well. I cleaned the lower screen and all looked good. All lines seemed clear. The fuel filter is new but is it supposed to be only 1/2 full? The fuel pumps were rebuilt when the carbs were re-done a year ago so I don't think they're the issue. This issue only happens above 5500rpm, all other times it runs like a champ. The fuel filter is placed correctly top to bottom but I'm not sure if direction matters. I guess I could (temporarily) bypass both the filter and check valve to see if that makes a difference. I've attached pictures. Not sure where to go next,

 

[QBhoy]

I pulled the fuel pick up today. The check valve was working well. I cleaned the lower screen and all looked good. All lines seemed clear. The fuel filter is new but is it supposed to be only 1/2 full? The fuel pumps were rebuilt when the carbs were re-done a year ago so I don't think they're the issue. This issue only happens above 5500rpm, all other times it runs like a champ. The fuel filter is placed correctly top to bottom but I'm not sure if direction matters. I guess I could (temporarily) bypass both the filter and check valve to see if that makes a difference. I've attached pictures. Not sure where to go next,

Hi. Just make sure the filter is going the right way. Easy to get back to front. I take it the compression is ok on the engine ? If so, might just need to go through the whole carbs and fuel System. Or try running it straight off a know. Good fuel source