No Throttle Response Past 1/4 Throttle

I'm working on a friend's 99 Royal Star XVZ13AT. I've checked for similar posts,but no answers found. The bike sat for a year and the carbs got clogged up so he asked me to clean them, it ran fine before he let it sit. I disassembled carbs and cleaned all the clogged ports and blew out all passages with air, replaced fuel inlet needles and reassembled with no problem. Spraying carb cleaner into carbs doesn't help it get past the stumble. Diaphrams all operate normal. Air filter is new, slides just start to flutter as throttle goes past 1/4. Any insight to similar problems would be appreciated. I'm going to start all over with cleaning the carbs. I've never seen a carb with O-rings under a main jet before. I have surely missed something but a little help would be nice. Thanks

I'm working on a friend's 99 Royal Star XVZ13AT. I've checked for similar posts,but no answers found. The bike sat for a year and the carbs got clogged up so he asked me to clean them, it ran fine before he let it sit. I disassembled carbs and cleaned all the clogged ports and blew out all passages with air, replaced fuel inlet needles and reassembled with no problem. Spraying carb cleaner into carbs doesn't help it get past the stumble. Diaphrams all operate normal. Air filter is new, slides just start to flutter as throttle goes past 1/4. Any insight to similar problems would be appreciated. I'm going to start all over with cleaning the carbs. I've never seen a carb with O-rings under a main jet before. I have surely missed something but a little help would be nice. Thanks

While you have it apart... replace the needles and seats part #4km-14107-15 you will need 4.

The o rings and the needle tip dry out and are the death of this engine.

while you had the rack apart to get one of the float pins out, it is very likely that you got the throttle position sensor out of proper position. $.02

report back with 12 bucks

mike

Would that not trip a fault in the self diagnosis system?

is it running on all 4? That's how my 1st gen acted when tci fried. I had let it set for a year before that happened.

Starts, idles great and runs fine until just after 1/4 throttle.

I'm reading up on how to check throttle pos sensor. Looks like checking resistances. I only tore down carbs enough to get bowls off, trying to prevent whatever problem I have now. All 4 slides flutter as throttle goes past 1/4.

The Clymer book says get resistance between blue and black/blue, 5000, then multiply by .13 and .15 to get adjustment range, 650-750. Next measure resistance between yellow and blue where I got 4.37??? Resistance between Yellow and black/blue was 700. Is wording wrong about which wires to test? 700 would be right in the middle of the spec.

I replaced needle valve and seats when I cleaned it.

Does it still have the stock air filters?

Does it still have the stock air filters?

Yes and new. Its all stock except BUB tips and they shouldn't require jetting change. That's the good thing about staying stock, all specs in manual should get bike running pretty good.

TPS was within spec but I adjusted towards lower end of spec like in forum tech section speaks of.

What would interrupt signal to diaphragms to make them flutter? Can I cuss now?

Take the air filters off and physically inspect them and the air passages.

I'm with Marcarl on the air flow. The bike sat for a long time so I would check the exhaust also. If you haven't touched the TPS, I doubt it's the culprit.

I had a similar issue with a 1st Gen I picked up a few years ago that sat for several years. Same thing, got it to start up after a little tinkering but it wouldn't rev at all. Kept starting it over and over, trying to rev it with no luck. Finally, out of the blue, it revved up and sounded pretty good. When I looked back, there was nesting material and acorns strewn all across the driveway behind the bike. Little critters just love exhaust pipes and air intakes.

I'm with Marcarl on the air flow. The bike sat for a long time so I would check the exhaust also. If you haven't touched the TPS, I doubt it's the culprit.

 

I had a similar issue with a 1st Gen I picked up a few years ago that sat for several years. Same thing, got it to start up after a little tinkering but it wouldn't rev at all. Kept starting it over and over, trying to rev it with no luck. Finally, out of the blue, it revved up and sounded pretty good. When I looked back, there was nesting material and acorns strewn all across the driveway behind the bike. Little critters just love exhaust pipes and air intakes.

I'm off to check the exhaust!

Just curious. Are you trying to run the motor without the air cleaner/assemblies on?

It won't run well at all....

Do check all the air passages from carbs back towards the air cleaners....should be clear, clean and tightly assembled.

Sounds like you've gone over most of the trouble areas. If the air system is good, then go back to the carb circuits. Pilot jets, etc.. The usual culprits for not getting engine to rev off of idle....

Good luck. Awaiting how this turns out....

It's got to be I put the O-rings in wrong place under the main jet.

My first thought would be a plugged up fuel filter??

OK, on Bike Bandit's parts diagram it shows a O-ring (#15) between main jet and main jet holder. Its little bitty. The base of the holder has metal washer to seal it, so does it go on main jet between the threads and the round head to seal against the holder?

THAT'S IT!!!!! That little O-ring goes around base of main jet to seal where it screws into main jet holder. Yippeeee!!!!

Glad you found it!! First place I would have headed would have been to the diaphrams to double check condition and completeness of components under them caps = probably the reason why it takes me 200 times longer to figure stuff like this out then most folks:big-grin-emoticon: