Hi all,
My 1985 Vf1000FE won’t rev above 6/7000 rpm in any gear. It feels like an electrical issue to me, almost like it’s hitting a rev limiter. From tickover to 6/7000 it pulls like a train with no issues. Does it when cold or hot/choke on or off.
Before I go looking, is this a common issue with VFs that could cause this or do I just start eliminating components as normal.
Cheers for any advice.
Nothing silly like a kinked fuel line or blocked filter maybe…?? Check the coils too, they often “split” between the secondary plug terminals and the spark will follow the point of least resistance. My RE had a split coil and was causing strange things to happen…replaced them with some high output 3ohm jobs, new ignitor boxes from Carmo, leads, plugs and plug caps… and all is good now.
Smithy.
Many thanks for the pointers. I’ll let you know how I get on!
By the way, where did you get your coils and HT leads from please?
Coils came from an Australian mob…“Tri-Spark”, here’s a link:
The plug leads I made from a length I bought on fleabay, you can buy it 2 meters at a time:
Smithy.
Update: So I changed the spark plugs, HT leads and caps and just for good measure changed the fuel lines/filter and air filter at the same time. Unfortunately the problem persists. Seems to get worse as the bike warms up. Coils don’t have any visible splits, but I’ve ordered some to try that next. Fingers crossed. If that doesn’t work I guess I’m looking at the ignitor boxes 
I’d be looking at the pulse generators, getting worse when heats up might be the giveaway. Coils may indeed be the issue, they don’t have to be split to cause issues…if originals, they are 40 years old.
I’ve now changed both coils as well and still have the problem. Just measured the pulse generator resistance and got 474/455 cold, and 571/543 hot. Not sure if that means they’re good or bad but I guess it’s the next thing to try. Anyone got a known good set of pulse gens they want to sell please?
Cheers, Steve
Pulse generators should be ~480ohms according to the manual.
Smithy.
Yes, 480 ohms. Doesn’t give a tolerance though in my manual? I would expect the resistance to change with heat, just not sure how much is acceptable. Anyway, I’ve sourced some used ones from Ebay, supposedly known to be working when removed. Fingers crossed that’ll sort it. Interestingly, the ones currently fitted must have been changed at some point as they’ve got the additional wire in the loom that would attach to the thermostat on later models I think.
In my experience ignition pickups that failed did so at temperature and worked once cold,they operated normally through the rev range until hot.
I bought a boldor many years ago that had sat in a garden for 3 years.With very little work it was up and running but would not rev over 7K.
To cut a long story boring,I fitted another set of carbs which cured the problem.
like yourself I was convinced it had to be electrical as it was such a definite cut off.
I was fortunate enough to have a stock of spares so went through the ignition system replacing everything to no avail.The carbs were a last ditch attempt after ruling out the fuel pump and pipe work.
Best regards Bif
Thanks for the info. I’m just waiting on the cover gasket to arrive and I’ll swap out the pickups as I’ve already bought them. If that doesn’t work I’ll pull the carbs and strip them before I start splurging on more electrical components.
What could fail on the carbs to do this? If the bike’s been laid up a long time, the slides may be stuck with fuel residue (I had that on a Yam TX750) or diaphragms split.
A good question,I stepped and cleaned the original carbs(pre my purchase of an ultrasonic bath)as best I could,no torn diaphragms and all passageways I could find blown through with carb cleaner.Float hight set and carbs refitted with no change.
Swapped the carbs and the bike pulled(and still does)all the way to the rev limiter
