'83 vf750f clutch not diengaging/bike running hot

Hiya. So I've ressurected my brothers 1983 750 interceptor from the dead but it still has some issues here and there. one that has been frustrating lately is that when the bike is hot the clutch is not fully disengaging and the bike will not want to move. This happens when I'm trying to get places and it sucks when all of a sudden I release the clutch lever and give her a little gas just to hear my engine rev. It is bad enough at times that I can fully release the clutch and the bike wont move at all. This only happens when the bike is hot which might be part of the problem. The bike seems to run pretty hot. On a normal summer day or night in stop and go traffic with the fan on and an oil cooler installed the temp gauge is almost always within a cm or so of the H. Should it be running this hot? I doubt it. The thermostat checked out fine and I have yet to check the fan switch but again, with the fans on the temp still gets that high but they may be kicking in later than they should. I havent gotten around to putting in an override switch yet but that isnt fixing the actual problem, just sort or working around it. Any ideas? I was thinking maybe something with the oil in the bike getting too hot then messing with the clutch plates in some way but I have no idea. I use castrol synthetic 10w40 with no oil additives. I have bled the clutch and messed with it a handful of times and it should be ok for the most part. The bike rides fine until it runs hot for a while. Any ideas would be appreciated. :0)

 

hi,
As said in a previous post, this is a structural problem for old (new) Vfr models. My VFR (750 F. '87) had a similar problem. I mounted a manual switch to start the fan before the temp reaches the red zone. At half/gauge temp I start the fan and every thing is ok : no boiling coolant, no loss of performance. The original fan switch starts around 90/95 C° that is too late for refreshing the engine when you are in urban cycle...
Try this : not expensive and sure method.
Lamps and have a good ride.
Carmine

 

I'll go ahead and give it a shot. I thought maybe there was something else I could do to help the overheating out but I've been meaning to put the switch in anyway. The question still remains though about the clutch not diengaging. Is this directly related to the bike running hot? That is my guess but I want to know for sure. Any ideas?

 

How are the clutch plates? Fiber and metal. Fiber will have a thickness spec. Metals will have a warp spec. Are the plates burnt, blue, or broken. Is the outter basket in good shape. All of its fingers, are the fingers grooved. Is the inner hub in good condition.Hey why don't you do a clutch inspection.

 

I looked over the clutch stuff a couple months ago and everything looked ok, nothing obvious. Again, the bike rides just fine until it runs hot for a while so whatever the issue I'm sure it is directly related to the heat. It could probably use a little clutch work but with only a month or less or riding for the season it wouldnt be worth it to put her out of commission to mess with it until maybe it goes in for hibernation. I just dont understand how the heat would affect the clutch besides to say maybe the heat is messing with the viscosity which in turn messes with the clutch plates. I need to understand before I'm satisfied but that might only come when I take it all apart. Thanks for the help :0)

 

See here: Clutch/PluggedReturnPort - SabMagFAQ

On the heating issue: CoolingSystem - SabMagFAQ

 

I had a friend back in the day, when our VF's were only a year or two old, that had this same issue. His bike was an '83, mine was an '84. His problem seemed to worse at high altitudes. He changed his clutch fluid to DOT 5 (Silicone) brake fluid and his problem went away. DOT 5 has a much higher boiling point and we figgured that was what made the diff. I always planned to change my fluid to DOT 5 but my bike never had that problem.

 

Hey Tinman...
Now that I think a little more about what I just posted, the problem we had was that the clutch would not release. It sounds like your problem is the opposite. We would not be able to get his bike in gear without it rolling and when you came to a stop with the bike still in gear it would want to creep or die. Dunno if there is any correlation between the two??? Bottom line is we had a problem with the cluch not actuating and we replaced the fluid with DOT 5 and it went away. Hope it helps.

 

"the bike rides just fine until it runs hot" There are several areas I would look at. First is the clutch slave cylinder on the side of the case. It could be a little gunked up after all these years and the steel piston could expand then bind and stick out when it gets hot. Just like sticking brake pucks. But there should be enough pressure from the pressure plate pushing the rod back I would think. The rod itself may be binding in the hole that goes thru the case cause by expansion of the case when it gets hot. The only other area would be the pressure plate and clutch spring that put tension on the discs. Unless the pressure plate is binding in the basket because it's expanding or the spring becomes weak once very hot. But that seems like a long shot to me without looking at it. I'd check the slave cylinder and rod first.

 

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Thanks for the replies everyone, good ideas to look in to. The cooling system should be doing just fine, assuming the fanstat switch is turning the fans on at the right temp (the fanstat being the only thing besides the pump I havent tested but the pump is obviously working). I cleaned out both radiators well enough with a flush kit, removed each and did as much as I could before putting them back on.

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The clutch has been cleaned up as well. When I got the bike the fluid that was in the clutch system had turned to a thick powdery substance (I have no idea what my brother put in it before I got it) after having sat for a good 17 years. I took the master and slave cylinder as much apart as possible and cleaned, greased and sealed everything back up. The return hole I cleaned out with some very thin craft wire I use for various projects here and there. It has been a while since I cleaned up everything but I have a vague recollection of having done a job that I was content with (though I am notorious for half-assing). Everything worked fine and save for adding a little fluid after the first couple rides (as everything settled into every last crevice) I have had no issues besides the one in question. I am interested in trying the dot 5 fluid idea but is this safe? I'm happy to give it a go if It wont harm anything. Besides taking everything apart I'm sort of lost as to what to do. The oil cooler I put on (has an oil mod type adapter between the filter and block) has been helping to keep the bike cooler but only really begins to make a difference when the bike is moving as it is mounted on the front forks and needs airflow. The other idea I got from responses to another post is that the lean condition I'm running right now could be heating the bike up a bit so once I get the mixture leveled maybe that would help things cool down a bit and hopefully help this clutch problem. Any other ideas? I'm open to anything. Thanks again :0)

 

No safety issues with DOT 5 that I know of. Commonly used in automotive restoration projects to help prevent moisture in system and corrosion related problems that come with older vehicles that sit for long periods of time. Also is used in high performance applications where excessive heat is encountered.

 

First, if you haven't had the radiator puke coolant from the cap, you're not overheating...the temp gauge may be off. With a fully functioning cooling system, an oil cooler is not necessary. You need to test every component in the cooling system. And once every component has been certified as functional, you need to have the system pressure tested to see if you have any leaks. Only then would I consider adding extra components.

Second, if you add DOT 5 to your brake system, you have to first flush out every single bit of DOT 4 fluid. They are incompatible.

 

If the "fluid" that was in the clutch release system was a white powdery substance, I would suggest another rebuild of the system. There really is not a good way to tell if you got ALL of the powder out with your original rebuild.

Would also be a great time to switch to the DOT 5 fluid, since the silicone-based DOT 5 will not mix with the mineral-based DOT 3/4.

I'd also pull that actuation rod, and check it for warping/bent-ness.

As far as the temperatur issue is concerned - these V4's just run hot... If i'm in stop and go traffic, my '96 will creep up on the H mark.

 

Heya. I added the race oil cooler because I got it for a reasonable deal and it is not an easy part to find. If it helps to cool down the bike a bit (which it does) then great, I'm all for it. It's not a solution to the problem, just means to the end.

The cooling system functions just fine with no leaks so far as I can tell. When I cleaned out the radiators and ran the flush through the system I removed all the hoses, cleaned them up and then put everything back together. I have checked on it regularly and I have no irregularities to speak of.

The dot 5 seems like a pretty good idea so I'll go ahead and get around to that maybe this weekend or so.

When I cleaned the clutch system up I pulled the master and slave cylinders and the lines and shot several cans of carb cleaner through everything, ran wire and other stuff through to get chunks out, cleaned with soap and water, dried everything then did it again. The rod was pulled out and was flawless so I put it back in after using a flashlight to poke around. I then tested everything, flushed it, filled it again, some bleeding and it has been that way for several months now. The only place I would imagine that the powdery substance could still be is in maybe some tiny passage in the master cylinder but I had cleaned it up pretty well. Sure though, I could give it another shot and see what I find so that will be next on my list if the dot 5 fluid doesnt seem to solve the problem or during the dot 4 flush.

I think I have a reasonable starting point now which is what I was hoping for. I'll give everything a once over and do the switch to dot 5. If anyone is kind enough to share any other ideas I'm all ears. Mucho thanks.

 

The cooling system needs to be pressurized to work correctly. You may have an "air" leak and will never know it. That's why you need the system pressure tested.

"The cooling system functions just fine"

However, you said in a previous post that you are not sure if the fanstat is turning on the fans.

Do the fan's work?
Does the fanstat work?
Does the thermostat work?
Does the radiator cap work?
Does the overflow hose to the coolant reservoir allow air into the system?

 

I would NOT use DOT5 fluid. It is made for racing where it gets changed often. Dot5 is silicone and does not absorb water/moisture it separates it. So the water/moisture will separate and settle to the bottom of the puck area and then corrosion starts. The only thing Dot5 has over Dot4 is the boiling point is higher. That's why race machines use it. Some things for racing are not good for the street. That was one of the cautions about Dot5 when it first came out. It's funny you don't see that anymore. Your clutch system does not get that hot to boil Dot4 brake fluid. Neither does 99% of street brakes. Dot4 absorbs moisture, that's why it turns redish brown.

 

no, the fanstat functions just fine, I stated that it may be turning the fans on later than it might have been designed to do, but I'm not sure. The fans kick in about 4/5 the way to the H which seems a little late to me but I didnt build the bike. I should have mentioned before that the radiator system was sealed with some radiator stop leak stuff, fluid flushed then refilled. This was done after the whole system chemical flush. The hoses were sealed with high temp silicone as I was nervous that an old system like this might leak but since all this, everything seems fine. I would imagine that I would see some sort of vapor from a high pressure air leak but I see nothing. I checked over everything earlier today at operating temp and nothing seems to have an issue which is not hard to tell as there are not many cooling system connections to exam. I will spray some gunk or put soap around the connections tomorrow to be positive.

Now I'm not sure about the Dot 5. I'll look up a little info to decide the best outcome. Thanks again.

 

Radiator stop leak is bad... Check your thermostat. It may be partially clogged. It should have a small bleed through hole to allow coolant through.

If you have an air leak, you won't see any high pressure air leak...the system will never pressurize.

If you have a leak from the radiator to the reserve bottle, what will happen is (as the coolant cools) the radiator will pull air - instead of coolant - back into the radiator. So the level of coolant in the radiator goes down, and the level of coolant in the reserve bottle goes up. Check both after a good hot ride.

The fanstat is supposed to turn the fans on when the coolant reaches about 191-197F. The only way to tell if the fanstat is turning on at the right temp, is to take it out, put it in a pot, and bring water to a boil while monitoring the temperature of the water. Or use an infrared thermometer and read the temp of the engine until the fans turn on. Harbor Freight has a cheap one.

The temp gauge should be looked at as a loose approximation of the engine temp.

 

Heya. After the stop leak was used I flushed the fluid then put new fluid in because I didnt want it causing problems. I checked the thermostat after the stop leak so its fine. I never checked the connections to the reserve tank so I'll go ahead and do that and maybe have a pressue test done. When I first got the bike going it would spew coolant from the cap which makes me think it was pressuring and once the cap was replaced I havent had a spewing issue but it couldnt hurt to do as you suggest and go for a pressure test. Do they make self pressure testers or do I just take it to a raditor shop?

I've been thinking about getting on IR thermo as they're neat little gadgets and I used to use them back when I was a server at a local italian place. I'll look into getting one.

I have been meaning to test the fanstat but I've just been lazy as I have to drain the coolant. I'll get around to doing it though but the IR thermo should save me the trouble. Thanks a million.