78 No acceleration in 5th gear

[Dr. Dave]

I have rebuilt the carbs and replaced the fuel pump. Throttle to rpm response is slow. In 5th gear going from 75mph to 80mph takes a mile or two. Any suggestions other than down shifting. In 5th gear the engine is only turning 4k to 4.5k.

[Earl43P]

I read back into your 2012 posts and have one simple suggestion.
Plumb an external fuel source raised about 5' straight into the carbs and see if it revs up any faster.
My thinking is that you have crud built up in the tank line's screens/petcock/fuel filter.
When you get the fuel pump to carbs line disconnected, spray some carb and choke cleaner deep into that line and capture what comes out into a white rag. Might find that a mess of crud is blocking fuel flow to your rebuilt carbs. Wouldn't hurt to drain the bowls and check that for crud.

I know that my tank was a mess way back when, but I never used it until it was cleaned and coated.
Won't even mention how cruddy my carbs were from it sitting all those years with gas.

[warhead_71]

Also... could be a stuck gas cap vent. If it's not venting correctly, you'll create a vacuum in the tank and it will starve your fuel. I soaked my cap in vinegar for a couple of days then cleaned it with a toothbrush... it came out looking like new.

Otherwise, it's cheap to find a decent used one on Ebay. Or you can go aftermarket and get a Stant 10810 fuel cap... I've read elsewhere they fit the GL1000. Most auto stores have them.

[Dr. Dave]

I have read through the comments. Checked the tank last Spring and changed the filter. Checked the exhaust head temperatures 190F on the left and 170F on the right. First thru fourth I can reach 7K but I do not like rapping it that high.

[ericheath]

So it goes to 7k in the first four gears, is it snappy powerful or is it taking a while to get there? A compression test would help diagnosis.