Sucking it dry???

[maparker]

'81 450 TX, just brought back to life, complete carb clean and rebuild, new arifilter and boots on the stock air box, no bowl vent lines from carb

I got the bike running very well, thanks in large part to all the people here who either gave me advice or from old threads that addressed similar issuses. I had something happen that I've never encountered before though: Friday afternoon I-70 ~75-80 mph W.O.T. heading up a nice little incline where it crosses a railroad track, bike loses all power and dies just like it ran out of gas. I'd just filled up so that wasn't the issuse. Coast to the side at the top of the over pass deadstick. (semis produce a lot of buffeting at 75mph when only 6 ft away 8O ). Crank and crank, no joy, sounds like its not getting gas? Turn it to prime for 15-20 seconds and it fires right up!

Did I suck the bowls dry running W.O.T. ? What can I do to prevent this? It ran fine the rest of the way home and had run great all day previously (see post about riding Boulder Canyon http://www.thegsresources.com/_forum...=408511#408511) Is this just because I'm pushing the absolute limits of what this little motor can do? Just hoping that there isn't any sort of problem. Sorry if this is long, but I wanted to set the stage. Any help is appreciated

Parker

[focus frenzy]

check the routing of the fuel line to the carbs, short and straight is best, if it has to loop up or has any kink in it it will have trouble flowing enough fuel to keep up with that demand.
also in line fuel filters will also restrict flow to varying degrees.

another possibility is a restriction in the tank vent (inside gas cap)

[Sandy]

Also check the vacuum hose from the fuel tap to see if it's got a split or leak somewhere.

[jimcor]

Petcock diaphragm could be bad too. Check to be sure fuel vent in cap is not clogged. When my 550 did this it was the petcock.

[83'GK]

Did the bike run OK again after you turned the petcock back to running position, or did you have to leave it in prime to get back home? Also, why do you not have the vent hoses on the carbs? It is my understanding that they need to be hooked up.

[maparker]

Yeah, once I got it started again I put it back to "on" and it was just fine the rest of the way home (~10 miles on back roads). So I think it is something with either the petcock or the gascap vent...Or pushing this little bike too hard!

I have the lines off the bowl vents b/c they were never on the bike since I've had it....I didn't replace them b/c numerous people have found them to be a source of problems in situations much like I'm describing, which is why I mentioned it in the first place!

So anybody else with a 450 have a better feel for the "limits" with this bike?

Thanks for the replys and any other advice is always appreciated

[Nerobro]

If I ran my 550 WOT, the petcock closes and the bike dies. Copierguys' 300, with long duration WOT will do teh same thing your bike does. If you're gonna be running WOT for a long period, using prime will prevent this issue.

[Cajun Cycler]

If this happens again remove the gas cap and listen for a suction sound. If it has one the gas cap vent is blocked. without air venting into the tank the engine will starve for gas. More than likely that is the culprit.

[Anonymous]

A) Its only probable not definate that this is a fuel problem

B) Check for a kinked vac line and a partly plugged filter

C) Do the same thing at the same place again trying with and without prime. If it quits in both positions, determine if the carbs are empty. If you are in prime when you check for fuel, there is a good chance that enough will have reached the carbs by the time you check that it will sque the results so do it when in "run"