Surging after hard (hi rpm) run through the gears

Hello all,

First time poster here, it says, although I thought I had done so before. Anyways ...

I am the proud owner of a 1984 VF750F Interceptor.

I recently overhauled the carbs, replaced my fuel filter, completed a valve adjustment and fixed a couple of coolant leaks I had. Afterwards I sync'd my carbs.

I managed to get everything together and out for a few shakedown runs.

Notes: After a hard (quick). high rpm run up through the gears and you settle down to a cruise she starts to surge like she's fuel starved. I have to say that running up there she's performing great!! Once there and cruising she starts to shudder some. After a bit ... feels like an eternity, but probably 30 seconds or so she's running smoothly again. When I'm accelerating normally there's no problem and I can get up higher speeds without any issues. I've tried this several times, each time same result.

I was thinking float height, but they're pretty well the same as they were before. I only had to adjust one really. And there was no issue like this before. Although I'm not hauling a$$ like that very often (almost never), it's not my riding style, if I had to accelerate hard to get back into traffic I don't want her to be surging and I'm sure on a longer high rpm run I'd be running out of fuel.

Collective thoughts?

I have to say that after the valve adjustment, it seems noisier. I don't have much to base this on as I'm trying to remember it from last summer to this year. I don't have anyone else to compare it to. I've had it out for a couple of good runs, one long day ride and it seems to perform great! Not running hot, accelerates nicely through the rpm range a little crisper than last year. The fuel economy seems off a bit though, might be because it's running properly this year over last ... other than the surging after a hard high rpm run up through the gears.

I like riding this bike.

Thoughts on the surging would be great. I'll do some web surfing on it to see what else I can find. I also have to replace a leaking fork seal (again). I replace both of them last summer before the riding season and the left one is leaking again. Thought I'd try the OEM ones this time.

On that note ... what weight of fork oil should I try this time? I was running 10wt Lucas Fork Oil. Seemed to be fine, as I mentioned before, I'm not an aggressive rider any more. I just like to sport tour my way around.

That's a long bit. I'll let you catch up for now. Time to get off to work to support this habit ... motorcycle tinkering.

Cheers, canuk_guy

 

From the symptoms maybe the tank vent is not breathing easily so the bike is starving for fuel when it's drinking lots accelerating, or maybe the fuel pump is not keeping up at the same point.

For your forks, take a very close look at the stanchions, you may have some rock dings that have cut the new seal. These usually have a raised edge that needs to be filed/sanded smooth. For a damper rod fork, 10W oil or ATF is the norm.

 

Aftermarket seals almost always don't seal.

I haven't ridden my 84 yet but it surges at idle because the fuel pump is only working intermittently right now. The contact is dirty I believe. Anyways the bike seems exceptionally sensitive to changes in the fuel level in the carbs.

 

Might i suggest that you try tuning each idle mixture screw according to the directions in the FSM ??

A setting too rich or too lean on any one can cause problems like yours.