97 valk bogs down and stalls after downshift at high 45- 65- speeds ..

[f6 white buffalo]

Hey Folks ,  get your thinking caps on

  last fall   I have had my 1998 1520  bog down and stall without being able to restart.... once  after downshifting from 4th to 3rd in the  65  mph range and once after sitting at a light with a severe downhill lie ..

since these occurrences maintenance work completed have been

complete cleaning of carbs
sinking of carbs
inspect and or replaced all vacuum and breather lines
60 k timing belt service
rebuild petcock
clean out tank thoroughly half a dozen times
check gas cap for clogs and back pressure
replace plugs on non vacuumed carb ports

took the bike out for the second time since getting back from the dealer and on a downshift from 4th to 3rd at 45 mph  she bogged down and quit  again, as soon as I pulled in the clutch at the next light she cut off ...tried starting her but she just wouldnt start  , 

after 5 mins I was able to get her started and goosed the throttle hard until she ran smooth again....eased her home on back roads and 2 miles from home took her up on the highway  and she ran ok...didn't downshift at high speed because towing in my area is wicked expensive

the dude I bought the bike from had told me that he was a serial downshifter and had a certain part replaced because of that

waiting on him to return a call to tell me what that part was

the dealer he uses sucks at answering questions about previous maintenance

this bike runs like Gold ...full power  , shifts great , runs out like a dream .....except for these few instances

any ideas out there before I turn her over to the dealer again

   thanks in advance

[Bighead]

Open your fuel cap and ride it with it open and see if it still happens.

[old2soon]

And if it does run with fuel cap open you MIGHT have a pinched vent tube at rear of tank. RIDE SAFE.

[signart]

+1 on advice above. Also, has stock fuel line set up been modified in any way? i.e line filter added, etc.

[f6 white buffalo]

hey guys,  in reading tech tips here .... I see that in the  desmog description it states glass packs contribute greatly to the  cause of back pressure when decelerating causing back pressure to build in the system and building up gases ..backing up into the smog equpt ?...is this a possible cause of the problem ...I have glass packs ....also , when people sell you things they tend to keep nuggets from you while trying to slide the truth in there without exposing what they choose to hide...the seller of this bike made a point to say 2 things ...that the dealer told him his glasspacks were ok but he saw some wear that may cause them to be replaced down the road .... and that he had to replace a part because of his downshifting prowess.....both of these 2 items are directly related to my problem ..the bike bogs down when downshifting at high speeds creating high pressure in the glass packs which are known to annoy smog gear ......is it the combination of eroding glasspacks , downshifting at higher speeds causing high back pressure and the smog equipment ...would a new exhaust system solve my problems ....discard the glasspacks and go to a Cobra exhaust ??...Im trying to digest the desmog procedure  fully before deciding to cut anything apart ...thx

[Hook#3287]

hey guys,  in reading tech tips here .... I see that in the  desmog description it states glass packs contribute greatly to the  cause of back pressure when decelerating causing back pressure to build in the system and building up gases ..backing up into the smog equpt ?...is this a possible cause of the problem ...I have glass packs ....also , when people sell you things they tend to keep nuggets from you while trying to slide the truth in there without exposing what they choose to hide...the seller of this bike made a point to say 2 things ...that the dealer told him his glasspacks were ok but he saw some wear that may cause them to be replaced down the road .... and that he had to replace a part because of his downshifting prowess.....both of these 2 items are directly related to my problem ..the bike bogs down when downshifting at high speeds creating high pressure in the glass packs which are known to annoy smog gear ......is it the combination of eroding glasspacks , downshifting at higher speeds causing high back pressure and the smog equipment ...would a new exhaust system solve my problems ....discard the glasspacks and go to a Cobra exhaust ??...Im trying to digest the desmog procedure  fully before deciding to cut anything apart ...thx

That would be a first I heard of that, but sounds like an acceptable reason for your issues.  There's a member here that sells very nice exhaust systems, MarkT.  He's a sponsor here and he might be able to help you out with those questions.

http://www.horseapple.com/Valkyrie/Valk_Products/M2W_Exhaust__System/m2w_exhaust__system.html

[Ricky-D]

That the exhaust system can cause the problem you describe is nonsense.

Look to the carburetors for a cure. The bogging down would indicate improper jetting and needle to me.

***

[Chrisj CMA]

I cannot imagine shifting to 3rd at 65mph on purpose.  That said, its your bike but that would max out the OEM petcock, maybe even exceed its capability to supply fuel at the rate required in that situation.  You could also be experiencing interference from the rev limiter as soon as you let the clutch out in third at 65mph.

If this is an important thing for you to do shifting to such a low gear at such speeds you may need a real fuel valve like a Pingel

[f6 white buffalo]

downshifting at 65 mph was necessary as I was cut off on the hiway and couldn't  slide to the middle lane so I clutched , matched revs ,applied  hand and foot break and prepared to recover at a lower speed to clear out in case there were dangers from behind. Someone decided from the fast lane that they had to have a big mac and went from the left to the entrance to the rest stop in a blink ..I was more worried about what was behind me then what was in front of me ....can you expand on your views about the rev limiter . The bike goes from working awesome to bogging down , to after a brief rest  working awesome ...it happened again today . I rode after that with the gas cap off to see if it was a clogged  venting cap...and it happened a gain, it bogged down with no cap on it ...I assume that takes a clogged cap out of the equation ....now the bike wont start  , the starter just cycles ...any clues

[R J]

What RPM are you downshifting at?

What is the RPM after the downshift?

Sounds like you might be hitting the Rev limiter.

I've hit it in a drag race a couple of times, low to 2nd gear..

When you hit it, it really cuts the RPM's down real quick.

[f6 white buffalo]

would hitting the rev limiter make her mimic starving for fuel and cause her to shut down . i FIND IT ODD THAT IT CHUGS ALONG BOGGING AND THEN AS SOON AS i PULL THE CLUTCH SHE CUTS OUT INSTANTLY .............I no longer think downshifting has anything to do with it . I had it happen twice concurrent with a downshift so that is what got me going in that direction. But today it bogged/ starved fuel / died without any downshifting scenario...it actually did it today as I worked through the gears getting up tpo speed on the on ramp ...within seconds it started starving for fuel/ making the sound it makes when you are fuel starved ...but twice I got it to run smooth and powerful simply by waiting a few minutes and then getting hard on the throttle as if I pushed something clear in a line or petcock ...going to have to break her all down again and start from scratch . Was trying to play process of elimination....dealer performed timing belt replacement with tensioners, synced freshly cleaned out carbs and set idle  , checked vacuum all around for draw , replace intake plugs that aren't hooked to vacuum lines ,  inspected fuel lines for leaks pr kinks , same with vacuum...would 16 year old glasspacks having worn themselves over time affect the jetting and carburetor functions here.  the dealer said carbs were synced , can you sync carbs with needle and jetting problems ..... was sure we had worked our way close to a solution...am going to now consider the items mentioned above and do the research on those ..has to be something stupid . I don't rev the bike to a high rpm, I'm an old cruiser type...moseying along ...I don't stomp on it ...thx

[Chrisj CMA]

Your petcock is not supplying enough fuel at higher speed.  Same happened to me and after a repair and repeat I just replaced that OEM thing with a Pingel.  No more problems

[f6 white buffalo]

Your petcock is not supplying enough fuel at higher speed.  Same happened to me and after a repair and repeat I just replaced that OEM thing with a Pingel.  No more problems

I researched the Pingel..Im doing that ...its an upgrade even if it doesnt work ...thats a simple decision ...thanks for the suggestion...will let you know if it works ....

[Willow]

Your petcock is not supplying enough fuel at higher speed.  Same happened to me and after a repair and repeat I just replaced that OEM thing with a Pingel.  No more problems

I researched the Pingel..Im doing that ...its an upgrade even if it doesnt work ...thats a simple decision ...thanks for the suggestion...will let you know if it works ....

You can do that if you choose.  Lots of people have.  You will be, however, fixing a problem you don't have.

[Chrisj CMA]

Your petcock is not supplying enough fuel at higher speed.  Same happened to me and after a repair and repeat I just replaced that OEM thing with a Pingel.  No more problems

I researched the Pingel..Im doing that ...its an upgrade even if it doesnt work ...thats a simple decision ...thanks for the suggestion...will let you know if it works ....

I think that is a good choice, especially since you said the fuel starvation was occurring even before you lengthened the fuel line.  That doesn't mean however, that the longer fuel line isn't adding to the problem....just make sure its straight, no sag to impede flow

[f6 white buffalo]

Your petcock is not supplying enough fuel at higher speed.  Same happened to me and after a repair and repeat I just replaced that OEM thing with a Pingel.  No more problems

I researched the Pingel..Im doing that ...its an upgrade even if it doesnt work ...thats a simple decision ...thanks for the suggestion...will let you know if it works ....

I think that is a good choice, especially since you said the fuel starvation was occurring even before you lengthened the fuel line.  That doesn't mean however, that the longer fuel line isn't adding to the problem....just make sure its straight, no sag to impede flow

I checked fuel line before pulling tank...oh yeh !....shes a little sagged     thanks for the heads up ..never would have guessed that ....

[f6 white buffalo]

Your petcock is not supplying enough fuel at higher speed.  Same happened to me and after a repair and repeat I just replaced that OEM thing with a Pingel.  No more problems

I researched the Pingel..Im doing that ...its an upgrade even if it doesnt work ...thats a simple decision ...thanks for the suggestion...will let you know if it works ....

I think that is a good choice, especially since you said the fuel starvation was occurring even before you lengthened the fuel line.  That doesn't mean however, that the longer fuel line isn't adding to the problem....just make sure its straight, no sag to impede flow

I checked fuel line before pulling tank...oh yeh !....shes a little sagged     thanks for the heads up ..never would have guessed that ....

and hopefully with the layout of the pingle it will be easier to connect  fuel line after tank is mounted ...had to do it before bolting down before because of sausage finger syndrome ...

[f6 white buffalo]

Your petcock is not supplying enough fuel at higher speed.  Same happened to me and after a repair and repeat I just replaced that OEM thing with a Pingel.  No more problems

I researched the Pingel..Im doing that ...its an upgrade even if it doesnt work ...thats a simple decision ...thanks for the suggestion...will let you know if it works ....

I think that is a good choice, especially since you said the fuel starvation was occurring even before you lengthened the fuel line.  That doesn't mean however, that the longer fuel line isn't adding to the problem....just make sure its straight, no sag to impede flow

update ...Pingle installed...gas and vac lines shortened and taut ...gas in bike ...still does not start

so I was playing around checking this trying that ...and put it in gear , pulled the clutch , tried to start it and the bike took off ...the clutch is now not engaging ...didnt see that coming ...never had a inkling of a clutch problem ....but if you look to my description of my earlier problems ,  when the bike would starve fuel and bog down , she would cut right our as soon as I pulled the clutch ...anyone have any idea ...will investigate the fuel system further in the morning but it seems my beautifully running bike has a clutch problem