Vacation is over... bad acceleration

Hello again. I took a long vacation from wrenching after some new problems came up at the end of last year. My 79/650/B3 was running tops all of last year until about 15 miles into a ride, going about 40-mph the motor started to slightly surge. At first I thought it was wind hitting me, but the feeling became more pronounced in the next couple miles. I pulled her over and towed her back home.

Things I have checked: valve clearance, points, timing, air/exhaust leaks. Getting ready to pulled the carbs for a cleaning and inspection. Will be replacing the parts in the fuel accelerator (once Z1 has them in stock).

Problem is mostly now under load, pulling from a stop sign in first. Have to work the clutch longer with more throttle until the bike is moving good. This tells me it's either asking for air or gas. Air screws are factory 1-5/8 turns out.

Anything here I might be missing? ... coils/wires/rectifier/battery/short?

Have you checked your spark advance?
Steve

Easy stuff first. Go for a ride till you feel the surging then pop the fuel filler loose to see if your tank is venting.
Bill

KZQ wrote: Easy stuff first. Go for a ride till you feel the surging then pop the fuel filler loose to see if your tank is venting.
Bill

+1 start simple
My buddy had this problem recently... he was just running out of gas and the hills made the problem more pronounced.

Do you have an inline fuel filter? The clear ones, with pleated paper filters, for cars, start to seal up after awhile.

-checked advance last year - will pull the plate off and give it a full inspection - thanks.
-fuel cap venting. I recently went through it, will take another look - thanks
-inline fuel filter looks clean, will replace with a new one I have on the shelf - thanks


Engine revs sweet in neutral all day long, problem only surfaces under load.

swest wrote: Have you checked your spark advance?
Steve

I am scratching the idea of going to a new electronic ignition. Thinking I'll buy coils first then the Dyna DS2-2 kit later. Instructions say at least 3 ohms coils. Can I run points on 3 ohms or will they fry? This would also replace the advance unit.

I should clarify:
The paper element doesn't get clogged with dirt, it seems to seal up with a layer of glue or something... as if the glue in the filter gets dissolved by gas, then deposited onto the paper, clogging it, even though it looks clean.

In this video you can see there is no flow until I pressurize the tank. A car's fuel pump would have more than enough pressure, but gravity doesn't seem to be enough.

If motor still runs sweetly till load is applied and you have checked all the usual suspects as mentioned.......this issue manifested itself suddenly and with the symptoms you describe, my inclination is to check the clutch / cable etc.

loudhvx wrote: I should clarify:
The paper element doesn't get clogged with dirt, it seems to seal up with a layer of glue or something... as if the glue in the filter gets dissolved by gas, then deposited onto the paper, clogging it, even though it looks clean.

In this video you can see there is no flow until I pressurize the tank. A car's fuel pump would have more than enough pressure, but gravity doesn't seem to be enough.

I agree that a bad fuel filter is trouble, but in my case the engine would most likely die out of fuel starvation at idle and better on throttle.

bluezbike wrote: If motor still runs sweetly till load is applied and you have checked all the usual suspects as mentioned.......this issue manifested itself suddenly and with the symptoms you describe, my inclination is to check the clutch / cable etc.

thanks bluez. This was my very first inclination. After the problem happened last year and I pulled her over, i noticed the engine was smooth with good response in neutral. I actually snapped one of the throttle cables trying to clear her out. Bought two new throttle cables to replace the factory ones and also a clutch cable for good measure. I have not installed the clutch cable - will do.

I changed the oil last year in case there was contamination causing clutch slip, with no actual difference. However when I took her out last week for the first time she was running fine again??? Heat, oil saturation --- clutch plates slipping? Maybe. I just want to go through all the usual easy suspects before pulling the clutch apart.

Would I be looking at new springs and a full set of plates? Thanks

LineArtist wrote: Hello again. I took a long vacation from wrenching after some new problems came up at the end of last year. My 79/650/B3 was running tops all of last year until about 15 miles into a ride, going about 40-mph the motor started to slightly surge. ?

Could be a lot of things, on mine it was caused by crap in the fuel tank going into a jet.

LineArtist wrote: Hello again. I took a long vacation from wrenching after some new problems came up at the end of last year. My 79/650/B3 was running tops all of last year until about 15 miles into a ride, going about 40-mph the motor started to slightly surge. At first I thought it was wind hitting me, but the feeling became more pronounced in the next couple miles. I pulled her over and towed her back home.

Things I have checked: valve clearance, points, timing, air/exhaust leaks. Getting ready to pulled the carbs for a cleaning and inspection. Will be replacing the parts in the fuel accelerator (once Z1 has them in stock).

Problem is mostly now under load, pulling from a stop sign in first. Have to work the clutch longer with more throttle until the bike is moving good. This tells me it's either asking for air or gas. Air screws are factory 1-5/8 turns out.

Anything here I might be missing? ... coils/wires/rectifier/battery/short?