Blaster top end issue

M

mplombardi8

Location
US
Took my 94 blaster 700 out today. Riva red pipe, Riva water box, ada head, mikuni 44 sbn. So I have a video I'll post. It's runs okay, I put in new plugs today and went for a ride. I was flying full speed, it was running great. Then as usual(this has happened before) towards the end of me riping around and starting to get tired, I head in and start loosing top end. It revs up and down and won't get up to speed. Starts at about a quarter throttle and does the same thing all the way up to full throttle. Let me know if you have suggestions. I rebuilt the carb with a mikuni kit. Hoping the pump was built correct l, which I am almost certain it is. Please help!

-Mike

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A

absledder

Location
Alberta
I'm by no means an expert but is it possible it's overheating? I only say that since it happens at the end of a ride.

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M

mplombardi8

Location
US
Thanks for the response. On the hose I was running cold hose water through it and when I was out riding I have a side through hull pisser that I usually feel the temp of to make sure it's not scalding hot. Heat soak could be an issue but this is leading me to believe it's a carb issue. Maybe pop off pressure or the pulse pump would cause that?

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A

absledder

Location
Alberta
Are your fuel lines near your exhaust? I'm new to skis but I know in the atv world I've heard of fuel boiling before it gets to the carbs which can cause intermittent issues? Like I said I really have no idea, just trying to think outside the box since you already rebuilt the carbs.

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M

mplombardi8

Location
US
Yea I'll check those and I'll check the temp while it's running. It did only happen after a little bit of riding so maybe it was hot. So I'll post back the results of checking what you've said thus far. Thanks.

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M

mplombardi8

Location
US
So I just started the ski and it does what happened in the video right away so I don't think overheating is the issue. Maybe the carb pump or pop off or electrical issue would cause that?

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M

MX429

Location
New Waverly, TX
Make sure the check valve and vent hose on your tank are passing air. It could be drawing a vacuum on the tank and starving for fuel if the tank is not breathing. It's a dangerous thing to have that happen. I lost two top ends from going lean once before I figured out it was such a simple problem causing it.
 
M

mplombardi8

Location
US
Great idea. So when I open the gas cap it makes a sound like it's sucking air back in. Should it? Is the tank supposed to be under vacuum or pressure? Or at equilibrium with use of a vent. This is a great think to check. Do you think I should run it on land with the cap open to test it? Lots of questions about this but I never thought to check the gas tank cause I'm not very sure how it works

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M

MX429

Location
New Waverly, TX
It should not make a sound. It sounds like the vent is stopped up. It needs to be able to breath air in as your fuel disappears. If it doesn't, a vacuum will be created that your diaphragm fuel pump will not be able to overcome and it will starve for fuel.
 
M

mplombardi8

Location
US
Great I hope this is my issue. I will give it a try in the morning. Thanks alot for the response I'll post back my result

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billglass

billglass

Location
usa
Can a exhaust leak on the riva red pipe really cause a blown piston?? Octane??? Just wondering for my own benefit also.. That red pipe is always coming loose..
 
M

mplombardi8

Location
US
I was tuning it and changing springs so the leak affected what I was doing but didn't cause anything untill I tuned too lean I bet

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