82 Maxim 650 question

[NewRiderMike]

I have a '82 Yamaha Maxim 650 that I am getting back on the road.

On top of the connectors from the carbs to the engine there is a port on each. On 1,2 and 4, this is capped off with a rubber cap. On #3, there is a tube with a clamp on the distant end, approximately 9 inches long. The tube was not connected to anything and I was hoping someone might be able to tell me what it should be connected to?

Thanks, Mike

[Aussie Steve]

Sounds like someone set it up for a carb sync and forgot, was too lazy, or more likely, lost the other cap.

These caps cover/seal vacuum ports used to set the syncronisation of the carbs. As long as they are sealed then there is no problem.

On my bike the tube you refer to goes to the pair valve to create the vacuum needed there. If you do not have a pair valve system then forget about the pipe.

The pair valve is a lumpy device that, on my bike, sits above the cylinders and has numerous tubes and wires going to and from it. If you have one of these there will be an obvious connector that the pipe from the carbs goes to.

Good luck

[NewRiderMike]

I greatly appreciate your response! I didn't see anything in my Hayes book on it. I am pretty sure I don't have the pair valve system but I will have to double check. Am I correct that I should remove the hose and cap it off if I don't?

Mike

[superdave07]

check the tube to the fuel pit %%%% and make sure you have vaccum to both valve this bike has a vaccum control to the pit %%%% for fuel control a neat little trick on this bike is to switch it to prime when you want full throttle fuel, the engine loses vaccum at full throttle but if you change the valve to prime you will have all the fuel you need.

[Aussie Steve]

Originally Posted by superdave07

check the tube to the fuel pit %%%% and make sure you have vaccum to both valve this bike has a vaccum control to the pit %%%% for fuel control a neat little trick on this bike is to switch it to prime when you want full throttle fuel, the engine loses vaccum at full throttle but if you change the valve to prime you will have all the fuel you need.

Not sure what you mean by the fuel pit...

as for running on prime you would have to remember to switch it back after riding you don't want to rely on the carb float needles keeping the fuel out. The pipe if removed will need a little cap at the carb nipple. I would expect the line to go somewhere though.

[Blade]

Originally Posted by Aussie Steve

Not sure what you mean by the fuel pit...

as for running on prime you would have to remember to switch it back after riding you don't want to rely on the carb float needles keeping the fuel out. The pipe if removed will need a little cap at the carb nipple. I would expect the line to go somewhere though.

He is talking about the fuel petcock on the gas tank. Some of them are also vacuum operated when in the on and reserve positions. Some have either prime or off positions too.

[Easy Rider]

Originally Posted by superdave07

check the tube to the fuel pit %%%% and make sure you have vaccum to both valve this bike has a vaccum control to the pit %%%% for fuel control

I had that thought too. If the petcock has been changed to one without the vacume control, that might be why the plugged hose is there.

As far as this goes:

" a neat little trick on this bike is to switch it to prime when you want full throttle fuel, the engine loses vaccum at full throttle but if you change the valve to prime you will have all the fuel you need."

Say what? This is a joke, right??
In case it's not.........this is what the float bowls are for. When you whip open the throttle, the vacume drops for just a second until the rpms pick up, then there is plenty of vacume again.
To sumarize: that's a total load of crap.

[NewRiderMike]

Thank you all.

As it turns out, there is a nipple for it on the back of the petcock, but it wasn't connected.

As my 'nym suggests, this is all new to me, grabbing one of the dreams of youth and trying to get better mpg since I can't replace my deceased Prius ... I got this bike with 8.9k miles on it for $500. Previous owner says that carb # 4 has a cross threaded needle and didn't want to deal with and a friend had given him a Nighthawk 550 so he didn't need it. I've bought some eBay carbs that are on the way, supposedly drained dry when the donor bike was "retired" - looked good and clean in the pics, anyways ... So hopefully I can just swap the new set in and they will already be synced - since I don't have a clue how to do that and I am having problems finding anyone around here who wants to work on a bike this old ... Thank goodness for Haynes and a little mechanical aptitude!

Worst case - I end up parting it out and getting one that works, but this one is so pretty and such low miles, I hope I can get it running, because I'll run it till the end. I have never been one of those who needs to swap for the latest and greatest. Reviews of the 650 Maxim were all great so I went by that.

Mike

[Aussie Steve]

Mike

The nipple is to supply vacuum to the fuel valve....can't understand why the bike runs without it being attached unless, as ER states, the valve has been replaced with an on/off one

A carb sync is not too difficult as long as you have access to a set of carb sticks or vacuum gauges... will talk you through it if the new set needs doing.

As for the crossthreaded needle jet careful drilling to remove the jet and you can now get thread restoration tools to fix the thread in the carb so you will have a good spare set.

Good luck with the Ebay set I have bought vintage stuff off there with no problems.

[NewRiderMike]

I got the "new" set of carbs for my bike and went over them, cleaning
them out as best I can with brake cleaner, checking the diaphram, etc.
I found that at some point a small amount of water had gotten into
them, probably after they were taken from the donor machine and
drained out, so that there was a little bit of residue and such in the
bowls. All the passages were clear though and I was able to get fluid
through them. The floats had "varnish" on them and stuck at first,
but moved freely after I worked them. It did look like they had been
drained properly when taken out of use.

I mounted the unit on the bike and set the tank valve to "prime". I
suspect that there may be a problem somewhere as leaving it on prime
for a minute to do something else, there was some overflow and leakage
... Does that mean one of the floats didn't close? I couldn't see how to remove the floats.

I tried to start it and it came really close at one point, purring
nicely for about 5 seconds then dying ... there were also a couple of loud
backfires ... but nothing sustainable.

I removed a couple of the spark plugs and they were quite black, so I
will have to replace those, but do you have any suggestions as to how
to proceed?

[Aussie Steve]

Mike

You do not have to replace the plugs just clean them up and they will be good to go. The prime position should only be left on for a very short time...sufficient to prime the carbs only. The overflow indicates one or more sticky float needles so attention in that area is probably a must. It could be that the float levels need looking at and or the needle tips may be stuffed.

The carbs may be out of sync and this will cause rough running, although there is no reason for them to be if they were removed carefully.

I would switch the fuel valve to the run position and get the motor running....if possible... to check out the carbs condition and state of setting before pulling anything apart.

The floats on my B12 are held in place by a small screw across the float pivot pin. They are very tight and need care when being removed. I suspect there is some form of thread locking compound in there.

Once removed the float and captive needle can be removed for further inspection. The needle tip is viton and very hard wearing but any kind of groove indicates replacment is needed and also the actual brass fitted valve may be worn.

Do one at a time to always have one or more for a reference.

The float should have a small tab for height adjustment. I site I have used suggests the tab can be bent...up or down depending on which way you want the float height to go... to reduce or increase the float height by a maximum of 1.5mm and no more.

I cannot remember the site but a Google search for CV carb tuning will locate it.

Good luck and keep us posted

[NewRiderMike]

Aussie Steve, et. al.,

Well, I got her running!

Turns out that a big part of it was the plugs - they were fouled. I talked to a mechanic who told me that before I put new plugs in, if they are fouled, to be sure to use a BBQ grill lighter to burn out any gas in the cylinders, otherwise they would immediately foul again. So I pulled the plugs, all were wet, used the lighter to burn out the gas, and put in new plugs. In the meantime, found in the original carb set that there was one jet and one enrichment circuit in two different carbs that were blocked. Got those cleared. The bowls and floats in the original carbs were in great shape, other than the two clogged items, so I went back to those. So finally she started up.

With the choke on, she was idling @ about 5000 RPM. I worked with the idle screw and got her down to a better range, but still have to leave the choke on a little or she will stall out. I am going to run some SeaFoam through her ... not having those little precision drill bits, I couldn't make sure that all of the jets/nozzles were at the exact right/fully cleared state, just that they *looked* clear shining a light through them. Hopefully the SeaFoam will clear out any lingering problems and I can get her to idle properly without choke.

Oh what a thrill to get out there on the road!!

I am amazed at the power it has. At 75 mph I am only running about 5,000 rpm - she doesn't redline until over 9K, and I have read some people say that they don't really come into their power until they are over 6K!! I seriously doubt that I will ever, ever wind her out in 5th gear ... That would be somewhere around 120 mph ... I don't want to know what the fine on that would be.

Michael