Ran fine, died and cannot get fuel. Rebuilt carb and still nothing

[eddie708]

check the carbs and pop off. u compression should be alright at 130.

 

[mact18]

I checked the pop off pressure with a high end bike pump with built in gauge. I realize it is not ideal, but its what I had. I got 21 psi. After looking at what it should be, I realize it is low. Would this cause my issue of the rpms not coming up and also cutting out as soon as you hit the gas?

How do I fix it, if it is the issue?

Also, when the ski is running and I try to give it gas, it starts to cut out and I can see exhaust fumes coming out the air filter. Is this an issue. I still really havnt figured out exactly why it stopped running in the first place. Can the rave (?) get messed up while it is running fine.


Thanks

 

[kicker]

I checked the pop off pressure with a high end bike pump with built in gauge. I realize it is not ideal, but its what I had. I got 21 psi. After looking at what it should be, I realize it is low. Would this cause my issue of the rpms not coming up and also cutting out as soon as you hit the gas?

How do I fix it, if it is the issue?
Thanks

A low pop with less then optimal compression could very well be the cause of your issue. The pop should be 23-43 which is a big spread, I would shoot for 30-35.
In order to change the pop you need to replace the spring for the needle valve to a strong spring. The GTI calls for a 80 gram spring orginally, it will be the black one. Can you tell what color the spring is that is in there? Generally there are 4 options
Shiny silver 65 gr
Black 80 g
Dull silver 95 g
Gold 115 g

 

[mact18]

I put the original one back in there after I rebuilt the carb and it didnt fix the issue. The original is a silver one, I believe a dull silver. I only had one spring that came in my rebuild kit and it was another silver one, but it is longer then the original spring. I tried the longer one and it didnt work, so went back to original.

I wasn't able to clean the jets the time I put in this new spring, so maybe that was the issue and I could try this spring and measure the pop off. If that doesn't work, then I guess order a black spring?

 

[mact18]

I tried the other spring, and it is less pop off pressure. I also noticed that going in the pulse line, it was full of oil. I am assuming that maybe the bottom of my case is full of oil. Any easy ways to get rid of it?

 

[kicker]

I tried the other spring, and it is less pop off pressure. I also noticed that going in the pulse line, it was full of oil. I am assuming that maybe the bottom of my case is full of oil. Any easy ways to get rid of it?

Take both plugs out and turn the engine over. Lay a rag over the holes so you dont spray everything. Dont crank the starter for more then 10-15 seconds at a time, then let it rest for a minute so you don't overheat it.

What color was the spring in the kit, the shiny silver 65 g spring looks like chrome when it is new. If it looks more like stainless steel or aluminium in color then it would be the 95 g spring, i would give that one a try. Also what was the color of the original spring.....Black?

 

[mact18]

color of original was dull silver. The one that came in my kit I think was more shiny. I just ordered an 80 gram spring online. Guess I will have to wait a few days.

Will check to see if I do have excess oil in the bottom. Is it common to have oil inside the pulse line pump of the carb?

 

[Sportster-2001-951C-Stock]

Anything that's been through the crankcase will also show up in the pulse line and fuel pump diaphragm, including water and/or oil. If your crankcase is extremely full of oil and you can't seem to get rid of enough you might try tilting the ski up on it's port side (or whichever side orients the cylinder exhaust ports down so oil can run out the exhaust port) while cranking with spark plugs removed might get more out that way. Just an idea assuming it might be possible.

The Mikuni 95gram silver spring is wound in the opposite direction of the other four carb diaphragm springs, my eyes never can distinguish shiny silver from dull silver.

While the carb is apart it's a good idea to carefully remove the kidney shaped metering plate from inside the fuel metering chamber under the metering diaphragm and shoot carb cleaner through both brass jets while watching inside the bore for a nice stream from the tiny ports, gum or corrosion in those ports restricts fuel flow and corrosion (mostly from salt) is tough to remove.

 

[kicker]

Turn the fuel selector off while trying to blow out the excess fluid in the crank.

Sent using Tapatalk

 

[Tberghold84]

When you rebuilt the carb did you adjust the pivot arm to be flush with carb body? If the arm is too high it could possibly get pushed on which wouldn't allow the needle and seat to seal properly. I'm not sure if this would cause your problems but it was just something that came to mind to check out.

 

[mact18]

Thanks for the thought, but yes I did adjust the pivot arm to be flush. I am awaiting the 80g spring for the carb. Does my ski with the 717 motor have the Rave valves? If it does would they cause my issue. The current issue I am experiencing is the ski starts, but rpms never come up and dies if I hit the gas or turn the idle screw in too far.

I was reading about the Rave valves. When I search for 97 GTI it is not finding anything, just the GTX. Ok I see that the 717 motor doesn't have the rave valves, so I guess I am back to just seeing if the spring in the carb makes a difference. After that I have no clue what else to look at.

 

[Sportster-2001-951C-Stock]

The current issue I am experiencing is the ski starts, but rpms never come up and dies if I hit the gas or turn the idle screw in too far.

That sounds like a lean-die to me, a heavier metering arm spring won't resolve such an issue. If your carb is supposed to have the black spring then by all means put one in there b/c going back to the correct spring is a must and if you haven't already, make sure the metering seat has the correct orifice size as well.

For an off-idle lean die, I would closely scrutinize the condition of the tiny bypass ports, one may be clogged. Also in a situation like that a slight amount of choke should compensate the lean spot by forcing the large ports to begin fueling earlier.

At idle all the fuel is coming through the idle circuit, then as the throttle is cracked open the bypass ports begin to flow for a good portion of the butterfly travel then finally the large high speed venturi ports begin flowing as the throttle is opened further. If you can't get off idle, it makes me think the bypass ports are clogged or maybe your fuel pump is barely working.

A plugged fuel tank vent valve can also cause fuel starvation, at first it doesn't happen as the fuel tank is at atmospheric pressure but if air cannot enter the tank through the vent valve to replace the fuel being consumed then eventually the fuel pump will lose it's ability to pump fuel as a slight vacuum forms inside the fuel tank. This can be tested for by unscrewing the fuel tank cap slightly, to allow the fuel tank to breath. If the problem goes away this tells you a plugged vent valve is the culprit.

On some of the really old skis the fuel pickup inside the fuel tank used a rubber hose that dropped down into the bottom of the tank for the fuel feed, those rubber hoses are known to rot off over time. Filling the fuel tank completely full so the point of pickup is submerged in fuel can help pinpoint this issue.

 

[Sportster-2001-951C-Stock]

I just read back through your thread and realized your plugs are wet with fuel, this is indicative of a very rich condition and probably your eyes are burning due to excess fuel as you stand next to the running ski. A too weak metering needle pop-off spring can cause this, as fuel control depends on the metering needle opening at the correct time, a weak spring advances this timing and opens the fuel chamber metering valve sooner, allowing the fuel to come on sooner.

If this is the case (that the carburetor is flooding the cylinders with fuel) then I must agree, the pop off is too low and the spring should be stronger. You also must have the correct size metering seat orifice diameter, the diameter is also a function of when the fuel metering needle pops open (pi*r^2*pressure) so either increasing the radius dimension of the metering seat orifice gives you a lower pop pressure as does reducing the spring pressure. If the needle pops open too easily then there will be more fuel in the intake.

BTW, it's the vacuum in the intake manifold that travels through the three sets of fuel ports and into the fuel chamber, which causes the round rubber metering diaphragm to move inward and push on the metering needle lever arm. As you already know, the metering needle must be off it's seat in order for fuel to enter the chamber. Thus the calibration of the carburetor is dependent on both the strength of the metering arm spring and the metering seat orifice size. Also important, is the geometry of the metering needle lever, sounds like you have it set correctly, flush with the fuel chamber bottom.

Many racers work diligently on this lever to manipulate it's geometry set up perfectly and minimize geometric inefficiencies.

Also, please use a high quality screwdriver of the correct size (usually #2 bit) that's not worn out and the tip flutes rounded over, to avoid damage to the screw heads. Somehow someone at the factory is great at getting them extremely tight. A bit of abrasive lapping compound or toothpaste on the screwdriver tip can help get a little extra bite that's sometimes needed.

 

[mact18]

Thanks for all the detailed information. I will definitely try everything you said as soon as my spring arrives. Really not happy with shipping options at Iboat. Less then 2 dollar spring cost 7 dollars to ship and 8 days to arrive. I think USPS would have been way cheaper and quicker, o-well not important. Either way I am sitting around and waiting. Thanks again for the help. Will update once it arrives.

 

[Sportster-2001-951C-Stock]

A quick check and it seems I cannot locate a better "to the door" price than that for the black spring, the part is higher and the shipping lower. I think you've done okay, fortunately you don't need 100 of them b/c you might not get any break on combined shipping!

This happens to me all the time, sometimes I feel like shipping a giant crate filled only with helium!

 

[mact18]

So I took it to the local shop and after 4 weeks they said that my timing rotary valve broke. They are suggesting I replace the motor since they think that metal could have went in the bottom end. Does this make sense? I could get it to run if I dumped gas in the carbs, it didnt run well, but continued to run.

Can I just replace the valve and take the chance of the metal. Dont want to replace a motor if I dont have to.

Thanks

 

[Strizzo]

If the rotary valve has skipped a tooth, or has been partially obstructed at some point, it will have at least shifted the brass gear on the crankshaft, which will disrupt the timing of the rotary valve. even if there aren't metal shavings in the rotary cavity, it will be difficult to get the valve re-timed. it sounds like something has gone through the rotary valve at some point which means that it is likely still inside the case. if whatever is still in the case, it will find its way into the piston at some point and tear more stuff up.

ask the mechanic to show you the rotary valve, i bet it has a nick in one of the edges from whatever it hit. someone on here has some good pictures of busted rotary valves.

 

[mact18]

I guess its the actual timing valve shaft that probably broke.

Should I definitely trash the motor or is this something that is worth fixing?

 

[Strizzo]

this is what the rotary shaft looks like. the only place it can break is at the brass gear on the end. if it breaks, it will leave brass shavings in the rotary valve cavity, and it will also shift/strip its mate on the crankshaft. there is no easy/cheap way to replace just the brass gears, you'd have to split the cases, rebuild the crankshaft with a new gear, clean everything up, and replace the rotary shaft and put a new valve in, at the least.

you can replace the whole motor with a 1 year warranty SBT for around 750 bucks plus shipping and core exchange. plus labor to replace the motor, you'll probably end up ahead compared to paying your mech to rebuild it with ??? warranty.

 

[mact18]

Thanks for the advice. I was hoping that it would be easier to fix and I could do it down the road when I had time. I think I am just going to sell it cheap to someone that wants a project.