VF1000F only running on 2&4

Hi Folks,

I'm getting pretty puzzled by this, and hoping someone can shed some light.

I bought a 1985 VF1000F in non-running condition, I'd like to 'restore' it and pretty it up if I can get it to run properly! The PO bought it not running as well, and he changed the needles and seats and float bowl gaskets. He also bought three CDI units and put new plugs in it. He said he had it running but only briefly and there was fuel pouring from the vent tubes. It seems he also replaced the carb mount boots, because they're nice and soft. My understanding is that the engine isn't original, and may well have been apart because one of the head cover bolts was snapped, so when I took the head cover off to extract the broken bit from the camshaft bearing cap, I found a loose cam cap bolt.

I've taken the carbs off and cleaned them and set the float heights. They were pretty clean but the floats were way off, so that explains the excess fuel. I also replaced the rear two plug wires and caps because the wires had come out of the caps. It'll start up okay and run on the front two, but not the rear two - those pipes just don't get hot. I understand it's not an uncommon problem, and after doing all the usual stuff like swapping the CDIs (both swapping the boxes on the bike and swapping all the spare boxes into the 1/3 position) and swapping the coils side to side, I simply can't get the rear two cylinders to run. I read on here that these carbs are notoriously difficult to get clean, so I took them off and did them again. I don't have an ultrasonic bath, but blew them thru with compressed air and I can poke wire through everything that should have a hole, and can't fault them.

Interestingly, I'm getting a tach signal, so doesn't that suggest that the coil for 1/3 is getting a signal, so should be firing? It seems to me that would rule out the pickup (which resistance tests okay) and the CDI. The coils both resistance test okay, and the 1/3 coil will run the front two cylinders, so that would seem okay. Both coils mark spark with the plugs out - the spark isn't nice and fat and blue like I'd like, but again, the front two are running...

I'd have thought that even if some aspect of the carbs is still not clean (like the idle/slow circuits), then it might start working okay at higher revs, but that's not the case - though the plugs may be too wet to fire by then. The plugs look wet when they come out.

It has resistor plugs in it at the moment, so I'll change them to non-resistor to see if that helps (not that it should), but otherwise it would seem that either the carbs are still dirty (don't know how), the valve timing is off, or there's a major mechanical issue that isn't obvious. I haven't compression tested it because my tester is acting up, but I'm working on that.

Any help anyone could offer would be greatly appreciated.

Steve.

 

It sounds like you've covered alot of the bases on this.

Check and clean all the coil ground returns, although if you are getting spark on all four plugs out of the bike it appears to be working.

Are the plugs wet or fouled--try fresh ones. If they foul again quickly then you've got a fuel issue (carb floats). Did you check the carb floats on the bench to ensure they cut off?

Did you clean the choke and pilot circuits well, how about the mixture adjust screws, also needles and seats of float valve look okay and clean?

 

Where in Canada are you located?

Did you check to see if you're really getting spark on 1/3? Do a visual inspection or hook up a tester to the plug wires.

You can take the plug wires off 2/4, then spray a bit of starter fluid into the 1/3 cylinders and see if it will fire up on those .. this will absolutely show you if you're getting spark or not.

If those turn out OK, then you know for sure it's a fueling issue and it's time to look even closer at the carbs.

OOC ... if the caps on the cam were loose, did you check to make sure that the cams were properly installed and aligned to TDC, and the timing correct???

 

Try swapping the Coils Left to Right (easy) and see if the problem follows a Coil.

 

Sounds like he already did in his first post.

 

Yup, I missed that,,.. both topics (Carbs & Ignition) are jumbled together.

I agree, the Cams may not be installed properly.
The Official Honda Manual is Wrong (I have one), the Online Manual I found is wrong, and I've heard the Clymer Manual is also wrong.
With Crank set to T1-3 All Cams Lettering (INF-EXF & INR-EXR) should face UP, and Cam Sprocket marks should line up with Cylinder Head edge.
If it was done "by the Book", it might be wrong.
I put a Chop Stick into the Spark Plug Hole and watch it while Rotating,,.. The Valve action should make sense.

I've repaired a few CDIs.
The Wiring into the board can develop "Top Hat" circular cracks, hard to see;

Can make a weak spark, ReSolder.
I've also saved another by replacing the main driving FET.

Pickups are probably Ok, since there is sparking.

 

Bingo, the valve timing is bad, thanks folks. The rear cams are installed one with the stamped lettering up, one down. I also think the exhaust cam is off a tooth, but that's easily fixed if it's coming back apart. The valve timing on those cylinders is currently Power stroke, Compression, Intake, Exhaust. That ain't going to work...

I am, however, a little embarrassed to admit that my compression tester is fine, I just didn't believe that both those cylinders were making zero compression. Turns out they are...

Thanks for the info on the CDIs, @VF1000fe, that'll be good to keep in my back pocket. I've repaired Yamaha ones in the past by replacing transistors too.

Thanks again, I'll check back when I've found some time to talk some sense into this top end.

 

BAM!!!

Glad you figured it out!

Sent from my SM-G930W8 using Tapatalk

 

The Rare Reverse Feature

Good Deal,,.. gotta keep these Ol'Gen1 Battlestars breathing fire.

The Cam Sprocket notches don't line up perfectly, but Close is good enough.
If its off by One Tooth, it will be obvious.
Sounds like the Cams were installed to provide a Reverse Feature, its a heavy bike to Backup.
Check the Torque on the Cam Sprocket Bolts.
I've set all my Valve Gaps to 7 thou. and I don't use the special tool.
But Do use 2 feeler gauges at once.
When installing the Cam Chain Tensioner, make sure the bottom end seats into the pocket.
There is a little U-shaped piece of metal in that pocket that can jump out or turn sideways.
If you look carefully down in there, you'll see a shiney U-shaped pocket.

Those Ignition Boxes can get an inch of water in them,,.. drill a couple small holes in the corners.
I trim 1/4" off the Spark Plug Wire ends to freshen up the connection.

Good Luck.

 

Success! But a somewhat hollow victory, because it looks like it needs rings - at least. Compression is 60PSI on the rear cylinders and slightly higher on the front, and climbs to 110PSI with a bore full of oil.

I'm not really sure what to do - I don't really have time to rebuild it this winter, I was hoping to get it running and then focus on the bodywork, which needs a lot. With compression figures that low, am I right in thinking I won't get away with just rings, and that it'll need a rebore as well? Can you even buy pistons & rings for these things any more? I might have to mothball it for a year and keep an eye out for a donor engine. VFR engine swap? Apparently it's possible...

 

How many miles?

 

No idea. 86,000km on the bike, but it's not the original engine.

 

It may not be the Rings.
The motors I've worked on still have the Factory Hone marks on the cylinders, even at 90,000km, though they are getting shiney.
But the Valve Seats!,,.. they get quite Pitted, specially the Exhaust. You might be losing seal there.
I just did Valve Lapping, a bunch of Head Porting, milled the head by 4-5thou, new Valve Stem Seals and slap it back togather.
Still burns a little oil (worn exhaust valves a little sloppy in the worn Guides), but it still can Snarl when asked.
It could still be the rings, if the motor oil was not changed enough.
Run it, see what happens, use some 20W-50.
Good Luck

 

This .... how dirty are the valve seats too?

 

Right, but the old trick of squirting oil down the bore to seal the rings worked to bring the compression from 60PSI to 110PSI, so that suggests to me that sorting out the heads won't be sufficient to solve the compression issue. It definitely needs to come apart for inspection, but until I have time to dedicate to it, I'm reluctant to spread it all over my garage, so I think I'll put it on the backburner for a little.

Thanks for all your help - on (back) to the next project.

 

This is true .... if you have the heads off, you might as well go the extra step and check it all out at once.