1979 R65 gasping in high revs

[CAMPOA]

Hi there,

i need some help.

My 1979 R65 runs well at low revs but when i revit a little bit more it starts gasping.

Already cleaned the carbs as the sound of it was really similar to a fuel faillure.

What can it be? what should i do to try to understand what is wrong?

Please help

[Warbucks]

Did you try installing a new inline fuel filter? I had the same problem on a car that I used to own. It would start and then die at higher RPM. The fuel filter appeared to be clean, but after cutting it open and washing it out with clean petrol I poured the petrol onto a piece of white paper kitchen towling. The fuel filter was full of crap, even though inspecting it externally it appeared to be clean and fuel was flowing through it. You can get one really cheap at an auto parts store.

Just out of curiosity, what was the condition of the diaphragms in the carbs?

[CAMPOA]

Thanks Warbuks!

All looked well in the carbs but i didn't went for a full dismount check.

I will try to check the fuel fiters to see if maybe the problem is there.

thanks

i will get back with news.

[CAMPOA]

I think that these chinese filters may be the problem.

Any idea if i can open them? To try to clean them?

[Warbucks]

It doesn't really matter where the filter was made. More to the point, how clean is the fuel that you are buying? By the look of those pics I'm willing to bet the filter is the problem. That black crap inside is most likely restricting the fuel flow. The filter on my car looked cleaner than that. You can open them up, but it won't go back together again. They're a throw away part and should be replaced periodically. How often I do not know, but I guess it would depend on how clean the tanks at the petrol station are. If the petrol station is an old one and they haven't replaced the old underground tanks in decades, the fuel will be severely contaminated. If you know of a petrol station nearby that has recently been built, I'd be purchasing fuel from there.

Throw it in the bin and replace it with a cheap new filter. Chinese filters are ok.

I wouldn't spend the cash on an OEM filter.

[CAMPOA]

Amazingly helpfull and reassuring! Thanks a lot Warbucks! Gasoline here is known to be messy. So that contributes for this. Probably have to change more often. My next challenge is going to be, where to find these arround here. But i will make my way!

Thanks a lot. Will let you know after i do the change.

Thanks

[montmil]

Besides replacing the in-line filter, I would encourage you to remove the fuel tank and drain whatever nasty gas is in there. Remove the petcock and see if there is a mesh filter attached. Disassemble the petcock and clean it.

Flush out the tank. Trash may be clogging up the petcock. Look for bits of the OEM tank liner flaking off. Rinse with water and allow the tank to dry out for a couple days or so prior to refit and fill. Depending on your fuel source, it might be necessary to filter the gas prior to topping up the bike's tank.

That's some mighty nasty junk in that filter. Check auto parts stores or even lawn mower shops for similar filters. Buy extras. Confirm fuel lines are not disintegrating.

Let us know what you discover.

[Bob_Roller]

If this was indeed caused by poor quality fuel, I would suggest getting a fine metal mesh filter that you can place in the fuel tank opening while refueling the bike .
Remove as much debris as you can, before the fuel ever gets in to the tank .
As has been suggested, clean the entire fuel system including both carbs .
Replace the fuel lines, as they are known to cause issues when they get old and hardened and start having the interior surface deteriorate clogging passageways in the carbs .

[montmil]

If this was indeed caused by poor quality fuel, I would suggest getting a fine metal mesh filter that you can place in the fuel tank opening while refueling the bike.

Stainless steel tea strainer comes to mind. Years ago, I built a fiberglas fuel tank for an EXP Category aircraft and "borrowed" a strainer from my wife's kitchen supplies to liberate the s/s mesh to bond over the tank's sump. "No, dear. I've not seen it."

[CAMPOA]

Besides replacing the in-line filter, I would encourage you to remove the fuel tank and drain whatever nasty gas is in there. Remove the petcock and see if there is a mesh filter attached. Disassemble the petcock and clean it.

Flush out the tank. Trash may be clogging up the petcock. Look for bits of the OEM tank liner flaking off. Rinse with water and allow the tank to dry out for a couple days or so prior to refit and fill. Depending on your fuel source, it might be necessary to filter the gas prior to topping up the bike's tank.

That's some mighty nasty junk in that filter. Check auto parts stores or even lawn mower shops for similar filters. Buy extras. Confirm fuel lines are not disintegrating.

Let us know what you discover.

Thanks Montmill.

About 3 months ago the tank was lined to correct the already scraping orginal paint and metal. I am pretty sure that the dirt in the filters that may be choking the bike in high revs are not from there.

Will try first to find new fuel line filters and then stop/continue the search.

[CAMPOA]

If this was indeed caused by poor quality fuel, I would suggest getting a fine metal mesh filter that you can place in the fuel tank opening while refueling the bike.

Stainless steel tea strainer comes to mind. Years ago, I built a fiberglas fuel tank for an EXP Category aircraft and "borrowed" a strainer from my wife's kitchen supplies to liberate the s/s mesh to bond over the tank's sump. "No, dear. I've not seen it."

Ahah!

Ingenious and very Mozambican like solution!! Will remember this one.

[CAMPOA]

If this was indeed caused by poor quality fuel, I would suggest getting a fine metal mesh filter that you can place in the fuel tank opening while refueling the bike .
Remove as much debris as you can, before the fuel ever gets in to the tank .
As has been suggested, clean the entire fuel system including both carbs .
Replace the fuel lines, as they are known to cause issues when they get old and hardened and start having the interior surface deteriorate clogging passageways in the carbs .

Thanks Bob Roller,

As a matter of fact, lines are already giving signs of deterioration. Will have to put that in the "check next" list. Just to be sure what the cause is, i will do things one at a time. First i will change the filters. Lests see...

Liked your idea of the mesh on the opening of the tank but, to be effective has to be realy fine, and, if it is really fine, wont it reduce the inflow so much that it will caus spiling when fueling up?

Probably will make an experiment, as i really like the concept.

Thanks!  

[montmil]

If this was indeed caused by poor quality fuel, I would suggest getting a fine metal mesh filter that you can place in the fuel tank opening while refueling the bike .
Remove as much debris as you can, before the fuel ever gets in to the tank .
As has been suggested, clean the entire fuel system including both carbs .
Replace the fuel lines, as they are known to cause issues when they get old and hardened and start having the interior surface deteriorate clogging passageways in the carbs .

Thanks Bob Roller,

As a matter of fact, lines are already giving signs of deterioration. Will have to put that in the "check next" list. Just to be sure what the cause is, i will do things one at a time. First i will change the filters. Lests see...

Liked your idea of the mesh on the opening of the tank but, to be effective has to be realy fine, and, if it is really fine, wont it reduce the inflow so much that it will caus spiling when fueling up?

Probably will make an experiment, as i really like the concept.

Thanks!  

Could be worse. During WWII in the CBI theatre, my old man was, on occasion, forced to filter avgas through a chamois to refill his C-47's tanks. Using 5-gallon tins of fuel, it took quite awhile to top off tanks but the fear of losing power over "The Hump" was encouragement enough to do so.

[Warbucks]

A cheap and easy way of filtering fuel before it goes into the tank is to steal a pair of your wife's stockings. Cut the legs off and put one of the "feet" inside the other and slip that over the nozzle at the fuel bowser. When you're done filling up, rinse it out with water and stash it somewhere under the seat to dry out for next time.

If ya haven't got a wife you'll have to buy them. When the girl at the checkout looks at you funny, you say "They're for my wife". She probably won't believe you. LOL

Or, you could say "What's wrong? Don't you think I've got the legs for them?"

[Bill Conquest]

That's an awesome idea..might have to get hitched up just to solve that problem..