Having had. 3rd gen viffer about 20 years ago, I've just returned to the V4 fold by picking up a tidy 4th gen with just 23k on the clock.
As you'd suspect with that sort of mileage, it's been stood for a number of years. The previous owner recommisioned it but when I got it, it ran fine until around 6500 rpm but then bogged down quite badly and didn't want to rev beyond that with any sense of urgency.
So I had the carbs off, gave them a thorough clean and replaced all the o rings. This improved things considerably but it still loses power, bogs and hesitates between 6.5k and 8.5k, when it clears its throat and gets going again.
The airfilter is new, the plugs were replaced when it was recommisioned so I am at a bit of a loss.
Any thoughts on what might be causing this would be much appreciated!
When you went through the carbs did you inspect the slides and diaphragms?? Look for holes in them Also Was the secondary air filter gone? I went through a week of hell trying to solve a loss of power problem. Found goo from deteriorated secondary air filter sucked into area between slide and carb body binding the slide. Good luck!
Stock or aftermarket exhaust ?? You checked rate of fuel flow by pulling the fuel line going to pump ?? You know how to check the condition of slide diaphragms and their correct installation by blowing air into the proper hole ??
Taking off a cap to check that a diaphragm is seated correctly, ain't the way to go since it's possible to dislodge it in the attempt. Much better to blow in some air using a finger against the slide to introduce some resistance to movement. **
Someone with better picture-posting ability than i will come along with better info on where to blow, i hope.
** I believe that a small hole in the rubber would still lift the slide, but some resistance (your finger lightly rubbing) would sort that out.
In the present case, you need to determine that slide diaphragms are in good condition and installed all proppa-like. If so, you'll probably need a JETKIT so you can tune the adjustable needles to eliminate the rough spot (probABLY TOO lean). Some of the evidence you submitted seems to indicate that slides are OK if it will reach upper rpms, so the flat spot looks to be most likely a midrange (needles) problem.
When you went through the carbs did you inspect the slides and diaphragms?? Look for holes in them Also Was the secondary air filter gone? I went through a week of hell trying to solve a loss of power problem. Found goo from deteriorated secondary air filter sucked into area between slide and carb body binding the slide. Good luck!
Second air filter? You mean the small filter on the right side of the bike which is connected with hose to the diaphragms' top area? If there's no filter there it works properly as well. Had same problem last year and it didn't solve it.
It has a Remus road legal full system.
I suspect a diaphragm may be the culprit. I plan to check them properly at the weekend.
I have no idea where to blow to check their operation so guidance would be appreciated!
Check the valve clearances. That solved the problem for me.
Could you upload a pictures of your bike with the Remus exhaust?
End of thread · 7 posts recoveredWayback Machine snapshot 11 Mar 2016