84 VF1000R number 1 cyl running hot

Back in the old days (well a year ago) when the R was running, I noticed the rear left cyl was running 20 centigrade hotter than the other 3. This was measured using one of the non-contact infra red thermometers on the jacket/block below the head.

What could the cause of this be?

When I checked the valves they were out a bit but not outside the specs.

 

mixture screw adjusted slightly leaner,
pilot jet slightly clogged,
smaller pilot jet than stock,
cracked intake rubber boot (slight air leak),
crusty inlet valve causing incorrect fuel level in bowl.

If the motorsickle has set up more than a few weeks then the carburetors are suspect of varnish, sludge and clogging unless you drained them.

 

^ what he said.

 

Drain and flush the cooling system using a product that cleans. Possible build-up with pockets of sludge around that cylinder, reducing heat transfer. Try opening all the several coolant drain points, inspecting waterpump internals for corrosion or wear. Or, as K-B suggests, poorly adjusted float level in that carb ?

 

Thanks for the replies. I will start working through the items next weekend.

I am getting a horrible feeling I will have to pull the carbs.

Noooooooo

 

In a moment of insanity I pulled the carbs yesterday and could not see any obvious problems. I already have a couple of new spare sets of carby insulators. I will replace them now as the old ones are fairly hard.

I have to own up to a really stupid act. I removed the mixture needle screws one by one, counting the turns to seat them (writing this on the side of the carby), then removing them and replacing the knackered oring with a new one.

Then on the last carb as I was hurrying to finish I forgot to screw it in and count. I have now set the mixture screws to the 2.25 turns out as specified by the book. Is it leaner when the screw is wound out or in?

Should that be close enough to ok to get the bike rideable? I have a set of four colourtune plugs I am going to try out on this bike eventually (supposedly they make setting the mixture a piece of cake).

 

Counter-clockwise is a richer idle mix. Instead of using book specs that are set for low emissions USA standards, most VFRs run better at lower speeds by going up to 3 turns out. Book specs are only a starting point, and careful tuning usually yields a different setting as optimal.

 

The gods of motorcycling have been on my side for once on this bike. After pulling the carbs and swearing I would take nothing else off, I discovered that both the coolant pipes coming out of each head had mysteriously fallen off (after the retaining screws and brackets were accidentally removed).

Wanting to flush the engine with some high flow water from the hose I re-installed the front end and wheeled it out of the shed into daylight for the first time in many months.

With the trigger gun on the hose I stuck it into one of the holes in the back of the front head, pulled the trigger and watched the water flow from the water pump (cover is off) and front cylinder drain hole.

This was repeated for the other front cyl and for the right rear cyl - some rusty stuff came out but mainly clean water. When I tried this trick on the number one cylinder (the "hot" one) the water went nowhere except back out of the hole and all over me. As I had 2 small boys in the yard I had to content myself with a couple of "damns" and "blasts" while they laughed themselves to the ground. No amount of surging the hose in the coolant pot would achieve any sort of flow.

Next came the exciting task of removing the chrome pipe and the two "cap, connecting pipe" sitting under the cylinder head oil pipes. In the cavity under the left cap between cyl 1 and 2 was a bit of muck but nothing too bad. When I tried to look into the gallery with a flexy torch it was obvious the gallery running to the number 1 cylinder was completely blocked with stuff.

Ten minutes with a cut and shaped coat hanger removed the blockage completely and now firing the hose into the port in the number 1 head results in as good a flow of water into the connector cap area as any of the other cylinders. So problem found by sheer bloody mindedness and fixed with a free coat hanger. If I Had really started using the bike at highway speeds I would almost certainly have seized the cylinder.

It was a great day for motorcycle maintenance at my place.

 

Good example of previous LACK of proper maintenance since coolant changes and flushes should be routine every few years and would have prevented that heating problem, possible engine damage.

Another example why you need to go through everything before riding your newest used bike.