Engine cuts out at high speed?

[nogrey]

Had a friend over yesterday to "fix" his Valk problems. His tires were at 14psi, he'd let it set a year without riding it, it was a mess. I told him it wasn't going to get fixed all in one sitting. The tires were easy. I took it for a ride and OH MY! It SUCKED! Low speed performance was OK, but could tell the slows needed work (probably a carb tear down and clean). What surprised me though was the lack of performance above 3K RPM. Usually, letting one sit gums up the slows, but the engine tends to regain composure as it begins to operate outside the slow mix, at around 2500-3000 RPM. Not this one. When you "get on it" stutters and misses like all get out. I dumped a full can of sea foam in the tank, which was nearly empty, and told him to fill it with fresh fuel and ride it awhile. I admit this is a hopeful first step. How would you proceed?

[old2soon]

Sitting for a year?? Punish the owner!  Air filter-plugs-plug wires-in tank filter-vacuum side of petcock-fuel lines-vacuum lines-pull timing belt cover and see if something-critter wise-has taken up residence. Could be spiders and wasps and such like. Get some B-12 Chem Tool-full can to a full tank of gasoline. You know the drill-under 2000 revs so it gets into the slow jets let sit etc-then run the snot out of it for at least 2 tanks treated with B-12. Check ALL the carb clamps. That will get ya started!!  RIDE SAFE.

[Patrick]

Yep, seems opposite of what normally happens. I too would continue with fresh and heavy doses of cleaner. But, I'd also recommend taking a good look at the petcock.

[Chrisj CMA]

I would suspect vacuum leaks with that stated performance, also the petcock may not be flowing enough gas........cracked vacuum line from #6 or leaky diaphragm sound likely

Vacuum leaks are found here:

-cracked vacuum lines
-dry-rotted caps on unused intakes
-loose intake manifold screws
-exhaust header nuts loose

[Red Diamond]

Don't want to sound sarcastic, but I never understood this complete carberator tear down thing. I purchase a Standard that had sat outside for 3-4 year under a cover, pulled the carb bank, replaced the jets, high and low, new carb bowl gaskets, pilot screw springs and o-rings and it ran great. While you are at it replace the intake o-rings and anyother vac hoses to be sure you have everything covered,, should run good for you.

[nogrey]

Thanks guys. I like the petcock as a possible. The other stuff is also likely but I need to check the filter screen and petcock to see if there is a flow issue. That would definitely do it. Vacuum is also a possible. The first time I tore down his carbs, it was strictly a clean. No money spent (per the owner) and I did it for free. Next time he comes over I'll have parts and just sell them to him as needed. I feel better when they leave running like they're supposed to.

[nogrey]

Don't want to sound sarcastic, but I never understood this complete carberator tear down thing. I purchase a Standard that had sat outside for 3-4 year under a cover, pulled the carb bank, replaced the jets, high and low, new carb bowl gaskets, pilot screw springs and o-rings and it ran great. While you are at it replace the intake o-rings and anyother vac hoses to be sure you have everything covered,, should run good for you.

It sounds like you're doing the same general thing the rest of us are doing. Just pulling the whole bank. I've never yet needed to go further than that. I've never had the need to replace a jet as they have always (knock on wood) cleaned up and performed just fine once all the varnish and dirt was removed from the rest of the carb. Pilot screw springs/washers and O rings seem to be another necessity on a bike that has sat a long time, as well as all the rotten hoses and timing belts.
I just finished a year long project on a '97 tourer that had been purchased, driven 2K miles, and then the owner died. The bike sat, outside, while the family fought over the guys possessions. It sat in probate for 16 years. Runs like a dream now.

[Red Diamond]

Don't want to sound sarcastic, but I never understood this complete carberator tear down thing. I purchase a Standard that had sat outside for 3-4 year under a cover, pulled the carb bank, replaced the jets, high and low, new carb bowl gaskets, pilot screw springs and o-rings and it ran great. While you are at it replace the intake o-rings and anyother vac hoses to be sure you have everything covered,, should run good for you.

It sounds like you're doing the same general thing the rest of us are doing. Just pulling the whole bank. I've never yet needed to go further than that. I've never had the need to replace a jet as they have always (knock on wood) cleaned up and performed just fine once all the varnish and dirt was removed from the rest of the carb. Pilot screw springs/washers and O rings seem to be another necessity on a bike that has sat a long time, as well as all the rotten hoses and timing belts.
I just finished a year long project on a '97 tourer that had been purchased, driven 2K miles, and then the owner died. The bike sat, outside, while the family fought over the guys possessions. It sat in probate for 16 years. Runs like a dream now.

Now that's a beauty, great job NG, just the kind I like. Thanks for the pic too.

[Firefighter]

Wouldn't run it too hard if its lean, be careful!

[gordonv]

My first thought was also either a vacuum leak or fuel starving, most likely a petcock issue.

Before I go to the trouble of tearing into the carbs, I would spend a little money on the B-12, Techron and Seafoam first.

I also don't know why you would be driving the bike higher than 3K rpm anyways, that gives you a nice economical cruising speed of 70 mph.

[nogrey]

Sitting for a year?? Punish the owner!  Air filter-plugs-plug wires-in tank filter-vacuum side of petcock-fuel lines-vacuum lines-pull timing belt cover and see if something-critter wise-has taken up residence. Could be spiders and wasps and such like. Get some B-12 Chem Tool-full can to a full tank of gasoline. You know the drill-under 2000 revs so it gets into the slow jets let sit etc-then run the snot out of it for at least 2 tanks treated with B-12. Check ALL the carb clamps. That will get ya started!!  RIDE SAFE.

I think the punishment pretty much fits the crime here. You throw your Valk in the closet for a year and deprive her of the attention she needs, she'll let you know all about it when you come back to your senses.