Is it possible to run an Automotive alternator on a xj?????

Hello everyone,
This is my first post as I am new to the site and the world of xj's, but not forums themselves. I am very into rock crawling (extreme 4 wheeling) and to make a long story short I am trying to use a xj650,750,etc... any Yamaha engine/transmission combo that has a shaft drive, work on a miniaturized 4 wheel drive vehicle.

MY MISSION:
My plan is to take off the alternator rotor along with the stator, basically take off everything that charges the motorcycle battery system and replace it with a custom machined fitting to go onto the pre-existing tapered alternator rotor shaft and connect it to a v-belt automotive alternator (around 60amps).

I need the alternator because i will also be using a power steering pump on the same v-belt in order to turn big tires and need a constant power take off supply for the pump. Since I will be loosing the motorcycle alternator charging system, I will need to replenish the power along with adding more amps for a stereo, lights, winch, etc... hence auto alternator.

MY MAIN CONCERN:
I know the motorcycle alternator system is on a different shaft than the ignition pickup coil, as the ignition pickup is on the crank. I am hoping since the ignition components are on a completely separate shaft to the alternating components, they will not be affected as long as a 12v charging system is maintained.

1) Will I be able to run a 12v auto alternator with built in regulator/rectifier to a auto 12v battery instead of the charging system that is currently on the Yamaha's now?

I only plan on using the ignition wiring along with the starter wiring from the motorcycle, as I can make another harness for everything else on the vehicle.

2) Does the ignition system only draw from the 12v battery?

If the ignition only draws from the 12v motorcycle battery, I don't see there being a problem as long as it has 12v power to draw from.

3) Does any of the Yamaha engine (shaft drive) combos have an alternator shaft with a key-way (machined grove down length of shaft) machined in?

the additional weight and resistance of the pump and alternator most likely will require a key-way for the systems v-belt pulley to not fail.


Thanks you for your interest and hopefully I worded this post okay so everyone can see my concerns.

 

Re: Is it possible to run an Automotive alternator on a xj??

Electrically you'd be fine.

Mechanically I can see a couple issues.

The alternator drive system is designed with a 19A alternator in mind. A larger alternator and power steering pump would be lots of extra torque. You could well find out that Yamaha didn't over engineer it enough for your purposes.

The stock alternator only puts a torsional load on the bearings. If I understand what you have in mind you'll be lengthening the shaft and tightening a belt against it. That's quite a side load that the bearings and case weren't designed for.

 

Would there also be issues with the carbs operating properly at extreme angles from upright? Just asking. Idk the answer.

 

Welcome Chris, interesting project !
You would custom machine a pulley for the crank end at the pick-up coils.
That leaves them exposed unless you are clever enough to make a cover, or enclose the belt. I don't think you'd need a big alternator at all unless you went crazy with the stereo amps.

Problem- - The 750 is only going to give about 45 Ft Lbs of torque, peaking around 7,000 RPM.
In first gear with a 4.129 rear gear you're going around 30 MPH
You'll need an additional 10:1 reduction (or so, round numbers here)
Why wouldn't you use a 1,500 or bigger V twin? (insurance wreck)
100 Ft torque available alot lower

 

Re: Is it possible to run an Automotive alternator on a xj??

Even more Basic than the alt issue: these Engines tend to run Hot .. Dohhh! being Air flow cooled. Motorcycle engines , they need reasoinable forward speed to dissipate engine heat
Stick one into a heavily loaded (4wheel drive) slo moving Gizmo and watch the engine overheat/sieze.

 

First off I appreciate everyone's quick responses

TIMEtoRIDE:
I actually want to machine a coupler fitting on the alternator shaft which is to the right or rear of the the crank. The motorcycle shaft drive would then mate up to a automotive transaxle (front wheel drive transmission and axle aka transaxle) out the two half-shafts that originally turned the front wheels, one half-shaft to the front axle and the other to the rear axle. This when all said and done would give me around 120:1 gear ratio meaning that the engine would turn 120 times for the tires to turn one time. Theoretically that's 120 x 45 ft Lbs, but not really due to efficiency losses. A standard 4x4 drive train in a jeep is about 40:1

Danilo:
Very good point I was afraid of this, I could possible run an electric fan to blow hot air away from the engine. I would love to find an engine of this range between 650-1000cc that is water cooled. The only problem is that the engine must be shaft driven and when looking down the shaft towards the transmission it must turn cw in order for the system to turn the transaxle and axles properly. I have looked at honda shaft drives but they turn ccw. I think kawasaki's and suzuki's turn cw but not sure.

MiCarl:
Very observant point. I have done shaft design before and know that the shaft is strong enough to handle the max torque (ft-lbs) of the engine and some, as the engine can only put out the max torque while the auto alternator and pump will put additional resistance on the shaft but never enough to physically hinder the shaft from moving. I am actually more worried about the failure point at the end of the shaft at the taper fit were both the coupler fitting and the shaft come together. I am used to dealing with key-ways so I will really have to figure out if the friction that the taper fit provided will be enough for the addition of the auto alternator and power steering pump. As for the bearing loading issue, I would actually use an additional bearing at the end of the extended shaft near the v-belt pulley allowing additional support to the entire shaft assembly and case.

xjdaver:
This has also been a long term question of mine. The engine will be turned opposite in my vehicle. So the front of the engine will be facing the rear of the vehicle. The engine/transmission will be behind me shaft drive facing towards the front of the vehicle going into the transaxle which will be located directly between the two seats in the center of the buggy. I have seen many people wheelie motorcycle as well as take turns pretty hard, but your right without centrifugal movement in a sharp turn like on a street bike and being planted on the side of a hill at a crazy angle in the vehicle, might cause some problems.

 

You asked if there would be an issue running this engine in an orienation/position at an angle other than what it was designed for? The answer is yes, there would be problems for the floats in the carbs.

Don't think you would be able to get it to run reliably because of difficulty setting floats.

 

You somehow have that backwards.
The top of the shaft turns TOWARD the tire on ALL shaft drive bikes.
The XJ has the shaft on the left of the bike, so looking at the rear it turns ccw.
The GoldWing / SilverWing has right side shaft drive, cw rotation, and they are water cooled. The GoldWing even has a substantial alternator.

Running carbs at extreme angles? Best bet is to adapt a Weber 2 barrel that's used in off road VW's. Re-jet for your engine. Piece of cake.

 

TimetoRide:
We are on the same page, I must have not worded that good enough. Yes the engine needs to rotate ccw when looking at the rear.

wamaxim:
there is a buggy already built with a 600cc honda street bike engine and it has done extremely well, the only difference is that it is turned sideways in his vehicle with the front of the engine facing to the west (when sitting in seat) on his buggy which would be 90 degrees off from how I would run the engine, this could be a factor because his hill climes and descents are acting as if the bike motor is leaning to either left or right on a sharp corner
here is the link:

http://www.pirate4x4.com/forum/showthread.php?t=334588

A couple quick questions:
I have access to a 650 maxim at a local junk yard and wanted to take the alternator rotor along with the rotor shaft

Will the rotor shaft come right out of the case once the bearing race held on by the 3 torque bolts is removed?

Also will that 650cc rotor shaft be compatible with other xjs engines, as i might start machining the rotor and rotor shaft without actually owning one of these bikes?

 

I think a 600 CC quad, 2WD or 4WD will eat your lunch. (except for the whole "rock crawling" thing)
Why not "one-up" your friends, since you are fabricating and build THIS thing and make sure it floats. Nobody has one.

http://maisonbisson.com/blog/post/13673 ... ian-truck/

Meanwhile, the alternator rotor is the same for '81-'83 Seca and Maxim 650 and 750, the 900, and maybe the 700's
Don't look at 550's or 1100's- - different engine family.