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
Getting nowhere fast here. Changed out the pickups and no difference. Stripped the carbs, ultrasonic cleaned them, checked float heights, replaced float needles, rebuilt and synchronized them, still no difference. Pulled the igniter units and found a couple of dry joints. Thought I must of found the problem, but no, still the same . To be honest, I’m out of ideas other than buying new igniter units from Carmo. Guess that’s next. It was a cheap bike to buy, but it’s getting expensive to fix!
Spent the day with VFPete at Stafford show yesterday and we were discussing your problem,we both think the carbs are still the culprit.
Ultrasonic cleaning is not the silver bullet many think it is,how well it works is down to many factors.Pulling the jets,slides and choke plungers out and dunking the whole bank into the cleaner has never worked for me,I have found that splitting the carbs up and cleaning them individually works best.
Each carb gets two cycles of 30mins at 60degrees using cleaning fluid mixed at 10:1.After the first cycle I rotate the carb 90 for the second cycle to cover any ultrasonic blind spots from the first cycle.
After spraying with wd40 every passageway is blown through with compressed air.It’s tedious work but worth the effort
Are there any forum members near to you that could lend a set of carbs to try?
I did split the carbs apart before the ultrasonic cleaning. Each carb got 10 mins before turning round/over a further 3 times, so 40 mins per carb at 50 degrees. I’m using a 10:1 mix of ultrasonic carb cleaner I’ve had good results with previously. Once out of the ultrasonic cleaner every passageway was cleaned with spray carb cleaner and then compressed air. Once back on the bike they synced easily, and I set up the pilot screws as per the Honda workshop manual. So all in all similar to what has worked for you. You may be right and they are the cause of the problem, and I’m happy to be proved wrong, but I still feel it’s electrical at this stage. I’ve ordered the Carmo igniter units so fingers crossed. In the meantime I checked compression which is fine and also tried a run with the fuel filler cap open in case it was causing a partial vacuum. Not sure where the tank vent is but I’m assuming it’s in the cap? If the igniter units don’t fix it, I’ll strip the carbs again and give it another go. I’m in Northamptonshire, UK. Not sure if there are any forum members nearby who may have access to a set of carbs I could try?
Let us know if the new units do the trick,if not I’m sure we can get a set of carbs to you.
Regards Bif
Got to agree with the above thorough cleaning methods. I have tried to clean VF carbs numerous times just using spray and air but always end up with pilot circuit not fully cleaned. Must be very tiny diameter circuit.
OK. So fitted the new ignition modules from Carmo and made absolutely no difference. I also cut out and rewired the 3 pin plug from the alternator/generator as the plug had melted at some point in the past, although it was still working (see pic)
