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RSRBOB, Technician
Category: Boat
Satisfied Customers: 1077
Experience:  Former Yamaha Factory Service Rep, Dlr Line Tech, Serv Mgr, G/M
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Hey Jeremy 93 Yamaha vxr pro 700 just put carb kit in it,

Customer Question

Hey Jeremy 93 Yamaha vxr pro 700 just put carb kit in it, replaced everything, got it to start but had use starter fluid but once running it ran fine. Turned it off and came back to it about 15 mins later, and it just wouldn't start, sprayed starter fluid again and started right up, did it again 15 mins later and same results.
Submitted: 5 months ago.
Category: Boat
Expert:  RSRBOB replied 5 months ago.
Hi and thank you for your quesiton.Check your inlet and return fuel line connections at the carb. The inlet line (from the fuel filter) plugs into the bottom fitting on the back of the carb. The top fitting is for the fuel return line going back to the tank. It is very common to get those reversed. When that happens, it has no where to draw fuel from because the return just dumps it in from the top of the tank. There are no pickups down in the fuel for it to draw from.RSRBOB
Customer: replied 5 months ago.
Yea I double checked that after hooking carb back up, lines are hooked up correctly.
Expert:  RSRBOB replied 5 months ago.
Thank you for the additional information.Since it runs on starter fluid, we know a few things. First, mechanically, it has enough compression to run. Secondly, it is getting spark so there is not an electrical issue. Third, it only runs when you supply an alternate fuel supply. This tells us what is missing and preventing this engine from running is it is not getting gas into the cylinders. If you are sure the lines are connected to the carb properly, the next thing to check would be to make sure there are no restrictions in the line, starting with the pickups in the tank. Take them out of the sleeve and make sure there are no issues with them. I would suggest blowing through the lines to ensure they are clear. The petcock can also be a restriction as well. Hopefully you have tried on and reserve both. If one and reserve do not make a difference, there could be debris in the outlet side of the petcock. Where I am going with all of this is we have the problem narrowed down to the system, just don't overlook any detail, no matter how minor it may appear. If the lines are clear all the way to the carb, then you need to pull the carb off again and inspect the internals. Make sure no diaphragm got crease or punctured. Check the setting on the low speed screw to make sure it is correct. Make sure the low speed jet screwed into the carb body is not restricted too.Let me know if you need more help.Thanks,RSRBOB
Customer: replied 5 months ago.
sir, before putting the carb back on I flushed the entire fuel system, every hose was blown thru with compressed air, all lines seem clear. You did bring up something I didn't check, the low speed jet screw, I remember messing with a screws on the carb there's 2 one one each side, not sure which ones which I'm sure that I turned them a few times not knowing what I'm doing. So which ones the low speed and where should it be set at? And is there anything else you would recommend ?
Customer: replied 5 months ago.
Ok adjusted the low speed still nothing. I was reading over your response, the engine runs fine once it starts but it needs a little spray of starter fluid to get it going, once it starts it runs on its own.
Expert:  RSRBOB replied 5 months ago.
Thank you for the additional information.The last problem you mentioned, hard starting the first time, is usually associated with high pop off pressure. The best solution to this would be to put one step softer spring for the float arm. Going from memory, I believe the stock spring rate is 110g. The next one down would be a 95g. Yamaha tends to like to run a lot of pop off pressure and it has been known to help the symptom you are experiencing by changing the spring.As far as the high speed and low speed screws, the easiest way to describe it is the low speed screw is on the same side of the carburetor as the cables are on. The high speed screw is on the opposite side. Settings for the low speed screw is 1 7/8 of a turn out from LIGHTLY seated. It is a brass screw seating against a cast aluminum housing so everything is very soft and easy to damage. Just run the screw in until it stops and back it out to the setting. If the ski hesitates upon rapid throttle movement, open the low speed the addition 1/4 turn. If it blubbers, where it doesn't want to accelerate but does not sound like it is going to die, turn it in 1/4 turn. That is the limit of its adjust ability. +/- 1/4 from 1 7/8. Now, if you do drop the spring tension on the float needle, you may need to lean the low speed screw out 1/4 turn to clean up acceleration off idle.The high speed screw is set at 1 5/8 turns out from lightly seated. Again, +/- 1/4 turn. Do not go below the minus 1/4 turn on the high speed. You could end up leaning it out too much and causing an engine seizure.Also, if you have not done a compression test since this problem has showed up, you need to do a compression test right away. This could be indicative of a mechanical problem too.ThanksRSRBOB

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