XS750 questions... again.

[Russ]

Alright, so that '77 XS750 that I bought... I was tinkering with it this weekend and all said and done, I got the old girl to fire up. I traced my prior electrical issues to a faulty ground wire... specifically the one running from the battery to the ground on the engine. I'm thinking the connection at the battery is to blame, but as there isn't much slack in the wire unless I re-route it, I think I should just replace it.. so my first question: What guage wire should I use to replace the ground? And is that something that would generally be easy to get?

 

Next question: Whoever owned this bike before me... I have no clue what this guy was thinking when he worked on it... but the airbox was in pieces, parts of it were missing... and there was no air filter. So I opted to remove the air box completely and go with the clamp on style pod filters. This left me with my new problem... the bike has a hose that ran from the back of the engine into the airbox... The shop manual states that this hose routes carbon emissions back through the carburators to be reburned. the original air box had a spot where this connected, but with the pod filters I'm stuck with leaving that hose hang loose. When I had it running, I was getting some nice smokey exhaust coming up out of this hose. Anyone got any ideas on what I can do with this? Should I just plug it or should I try to fabricate something to cycle it back into the carbs?

 

Final question: once again, no clue what the previous owner was thinking, but the wires to all the lights (brakelight, headlight, turn signals) have the grounds all spliced together into one ground. And the guy evidently didn't know what to do with it, so he wrapped it in electrical tape and left it hanging loose. I jury-rigged a wire to it and connected it to ground and amazingly enough, all my lights that I thought were dead came to life! so now for the question: Do I just ground this to my battery or should I run a new wire down to the engine ground or just ground it to the frame?

 

Thanks in advance for ya'lls help. I really appreciate it!

[Squidley]

Alright, so that '77 XS750 that I bought... I was tinkering with it this weekend and all said and done, I got the old girl to fire up. I traced my prior electrical issues to a faulty ground wire... specifically the one running from the battery to the ground on the engine. I'm thinking the connection at the battery is to blame, but as there isn't much slack in the wire unless I re-route it, I think I should just replace it.. so my first question: What guage wire should I use to replace the ground? And is that something that would generally be easy to get? I use 4 gauge on the cable upgrades on the Ventures, that will be plenty enough for you. I imagine you might be able to hit an autoparts store and buy a premade length. If you want I could possibly make you a cable if you give me a measurement length.

 

Next question: Whoever owned this bike before me... I have no clue what this guy was thinking when he worked on it... but the airbox was in pieces, parts of it were missing... and there was no air filter. So I opted to remove the air box completely and go with the clamp on style pod filters. This left me with my new problem... the bike has a hose that ran from the back of the engine into the airbox... The shop manual states that this hose routes carbon emissions back through the carburators to be reburned. the original air box had a spot where this connected, but with the pod filters I'm stuck with leaving that hose hang loose. When I had it running, I was getting some nice smokey exhaust coming up out of this hose. Anyone got any ideas on what I can do with this? Should I just plug it or should I try to fabricate something to cycle it back into the carbs? This is just my thoughts and might not be the right answer. I would get a vacuume nipple cover and clamp it on. Now mind you I dont know if this will pressurize the crankcase. Other with better knowledge of this will chime in I'm sure. You might want to start looking for an airbox on ebay.

 

Final question: once again, no clue what the previous owner was thinking, but the wires to all the lights (brakelight, headlight, turn signals) have the grounds all spliced together into one ground. And the guy evidently didn't know what to do with it, so he wrapped it in electrical tape and left it hanging loose. I jury-rigged a wire to it and connected it to ground and amazingly enough, all my lights that I thought were dead came to life! so now for the question: Do I just ground this to my battery or should I run a new wire down to the engine ground or just ground it to the frame? I personally would go with the battery as it is a solid ground. Dont mess with possibly loosing the lights over something like that. Make sure if you keep them all wired together that you solder them and heat shrink it. Keep the corrosion out and have a bit more piece of mind....just .02 worth from me.

 

Thanks in advance for ya'lls help. I really appreciate it!

 

Squid

[hlange]

On qusetion #2:

DO NOT PLUG THAT HOSE!!! It is the crankcase vent. Just make sure that it runs higher then the crankcase and if you want you can install a vent filter on it it keep vermin out. A minor amount of "smoke" coming from it is normal. You may find that you are running richer with the pods then the stock airbox, especially if you are running an after market exhaust.

 

On question #3:

http://www.yamaha-triples.org/library/misc/750sf/750sf_cable.pdf shows the cable routing for the XS750SF, yours will be simular. I would keep it as close to stck as possible to make future troubleshooting easier.

 

You may find the XS750/850 website helpful. http://www.yamaha-triples.org/portal.asp

[Gearhead]

Regarding #2, follow Hlange's advice. Definitely install a breather filter though. These are available at Autozone or similar place. In fact, you may be able to just put a very short hose on the nipple on the engine where this hose connects, and install the filter right there.

 

As for #3, most loads are grounded to the frame. Obviously, your frame and engine ground needs to be sound. You would have a lot of extra wire if you ground everything back to the battery. Not that it would be wrong that way, but overkill IMHO.

 

Jeremy

[V7Goose]

If you are seeing visible exhaust gasses from that crankcase breather, your rings are shot. There is no need for it to be connected to the intake, but that does reduce pollution. Make sure the engine has a functioning PCV valve; if not go get one from a junk yard from any engine (or your buddy's car!). Just make sure you can hear it rattle when you shake it and you can only suck/blow through it in one direction. Put this in the hose so that the air can get out but not back in. If you are going to run the bike that way instead of doing a top end job, make sure you change the oil more often. Those hot combustion gasses carry a lot of contaminants, and they will oxidize your oil faster too.

 

Does the bike have electric start? If so, you need a bigger ground cable than otherwise. 4 gauge should be fine. Just go to any auto parts store and tell the counter guy you need a battery ground cable about x long. If no electric start, 10 gauge should be fine. Good luck,

Goose

[hlange]

There is no PCV valve installed on a Yamaha XS750. The crankcase breather hose is open to the crankcase so that air may flow both directions depending on the conditions. If you install a PCV valve then the engine may suck oil when it cools down. A light amount of misting, "fog", "smoke" from the crankcase breather hose is normal. You should be able to judge the condition of rings using a compression tester.