GS750/VW Reverse Trike...Help needed from GS experts!!!

[aaronbev79]

Have a look for some 850 barrels and head just check the stud patters before you buy a cheap way to get some more HP apart from that its time to open your wallet i had some o/s s/steel valves made through Buzz at Dynoman at about $45 each if it still has the points ignition change that for sure Dyna-s is a reasonably cheap straight replacement but speed is a matter of money i am sorry to say,

Yeah -- I'm probably going to upgrade the ignition eventually. But I have so many things to build and fabricate for this bike that my ONLY concern at this point is reliability -- which I think is based primarily on how I rebuild the clutch and what I decide to do with gearing.

Do you guys honestly think that this motor is USELESS for this project? If so, I'll sell the bike on ebay and try to buy a CB750 or a KZ750 for the project. I know that a 750 is more than big enough for my speed/acceleration goals -- based on other reverse trikes I've seen -- so if you guys think the GS is REALLY that bad of a motor I'll sell it and look for another.

Otherwise, I would appreciate help with THIS motor as it currently is. Is there anyone on this board who's willing to step up and defend the GS750 for this project?

 

[spyug]

Well more is usually better but as you say it is going to cost more to step up to a litre or more. I'm happy as a clam with my 750. With about 670 pounds fully fueled and me on board it moves smartly enough for around town or highway. Its no quarter mile maniac but thats not what turns my crank anyway.

If you can bring your rig in at 700 or 800 pounds with the right gearing it won't be a rocket but it will move smartly enough to be entertaining. Besides you are building it for the twisties not a straightline. Being down with your butt a few inches off the pavement the sensation of speed will be tons of fun....I'm going to be jealous.

The fella on the website with the morgan look alike would be a good one to talk to about performance. With that Honda mill he's probably putting out no more than 40/45 horse and he can't be that light . I'll bet he's happy enough.

I'd go for it. If its not what you want sell and do it again til you get it right:dancing:

Let us know what you decide to do.

Cheers,
spyug

 

[aaronbev79]

Well more is usually better but as you say it is going to cost more to step up to a litre or more. I'm happy as a clam with my 750. With about 670 pounds fully fueled and me on board it moves smartly enough for around town or highway. Its no quarter mile maniac but thats not what turns my crank anyway.

If you can bring your rig in at 700 or 800 pounds with the right gearing it won't be a rocket but it will move smartly enough to be entertaining. Besides you are building it for the twisties not a straightline. Being down with your butt a few inches off the pavement the sensation of speed will be tons of fun....I'm going to be jealous.

The fella on the website with the morgan look alike would be a good one to talk to about performance. With that Honda mill he's probably putting out no more than 40/45 horse and he can't be that light . I'll bet he's happy enough.

I'd go for it. If its not what you want sell and do it again til you get it right:dancing:

Let us know what you decide to do.

Cheers,
spyug

Thanks for the support. Since I got such a good deal on a complete, great running bike with a title, I'm going to stay with the 750...I was just a bit disappointed that so many GS guys have apparently very little faith in the 750 version of their motors.

63hp for 700lbs is an aweful lot -- that's the same power to weight ratio as a 5.0 Mustang. And then, after improving the low end by messing with gear ratios, I should have plenty of acceleration/power for what I want. I'm not going to drag race this thing -- at most a may do an autocross at some point -- but my extreme handling capabilities will be my advantage in that case.

The GS750 is listed as having a top speed of 120 or so -- but I am fine with a top speed of 85-90 at the most -- that's how much I want to reduce my high-end. What do you guys think?

 

[scrapper]

I don't know if it will help but I belong to a forum, www.explorerforum.com. This is ford trucks not bikes.They have a couple of different formulas for figuring out gear ratios and tire size. It sound like a real fun ride, Good Luck

 

[Mark Harrop]

I've got an oddball project in the works too with an 1100g motor that will be in a position to overheat as well....

I guess there is only one way to find out, and if you find a cheap cyl. head temp gauge, let me know.

 

[salty_monk]

The GS engine is a great engine & will likely have more power than equivalent CB or KZ & be as or more longlasting. My whole point is you build these cars to be a blast.. I know from experience you're going to want more power later but switching to a 1000 or 1100 or even 1150 motor later will probably not be a lot of work!

This is how I know you'll want more power...

 

[salty_monk]

These two are 2 litre, 4 cyinder Ford powered. They have about 100hp at the wheels & about the same in torque (130hp flywheel). I have driven them with 180hp flywheel... you still want more!

Whatever engine you use it will be fun but you'll put the bigger one in eventually!

If you are set on the 750, I would at least build it with a 1100 motor in mind!

The red one was my first one.. sold that but still have the black one back in England. That trackday above was on my honeymoon!!

With the bad aerodynamics these cars will top out at around 115mph. 0-60 is about 6.5secs, weight is about 1500lb.

Dan

 

[aaronbev79]

I appreciate your advice -- I REALLY do. But I think you're missing my point. I am not going to spend any more money on my motor at this point. I have all of the major parts for this build purchased already, and I am going to start building within the month. All that I have left to purchase is steel, and some nickel and dime stuff here and there.

So unless you have an 1100cc motor that you want to trade me, I'm not interested in anymore advice that sounds like this: "get a bigger motor."

I'M STAYING WITH A 750CC MOTOR.

 

[aaronbev79]

These two are 2 litre, 4 cyinder Ford powered. They have about 100hp at the wheels & about the same in torque (130hp flywheel). I have driven them with 180hp flywheel... you still want more!

Whatever engine you use it will be fun but you'll put the bigger one in eventually!

If you are set on the 750, I would at least build it with a 1100 motor in mind!

The red one was my first one.. sold that but still have the black one back in England. That trackday above was on my honeymoon!!

With the bad aerodynamics these cars will top out at around 115mph. 0-60 is about 6.5secs, weight is about 1500lb.

Dan

Thanks again, but if you do the math, 63hp with 800 lbs is a better power to weight ratio than 100hp with 1500lbs. The Rayvolution EVO -- the car that I am copying -- weighs just over 800 lbs and has a 750cc motor. Granted, my motor is not as good as a GSXR, but what I don't have in power I will try to make up some-what with gearing. And what I don't have otherwise, I will not worry about since I'm going to spend about $2000 total on this project since I'm building it myself.

How much do you spend on your Lotus cars? I bet I will spend a fraction and have a hell of a time with my cheap 750cc engine.

Now, if we could get back to discussing the GS750 I would appreciate it. I am currently running the numbers to purchase my rear sprocket, and I will run them past you guys and see what you think. Like I said, I will probably put my high-end somewhere in the range of 90mph. Hopefully that will give me plenty of low-end acceleration.

 

[fast pom]

The GS engins are almost bullet proof coming as they do with a roller crank my 30 year old bike still runs strong, The concern with the clutch is that apart from improved plates and springs there is little you can do for them unlike the 1000 and the 4 valve 1100 that are widely used in drag racing and a whole mess of after market clutches . I have no experance with putting bike engines in car buy how ever light are still way more KGs than a bike plus extra traction from a larger tyre footprint i would be a little worried about the 750 clutch. Sorry dont want to be neg on this but it would be a crying shame to put all the work in to be let down.
My advice sell the 750 and look for an early 4 valve 1100 {GSX] as i know them with the roller crank. Good Luck

 

[aaronbev79]

I have quite a bit of experience with small motors, gearing, and big tires/weight.

I own a Suzuki Samurai with a 1300cc engine. It's a 4x4 vehicle with 26" tires stock, and it weighs about 1800lbs stock. After I was done with it I had 33" tires and it weighed somewhere around 3500 lbs with winches, new heavy duty bumpers, and a custom half-cab.

BUT, I kept the stock motor. What made the difference? Gearing. With the stock gearing I was eating up clutches like crazy, but after going to a much lower gear ratio, my motor was moving those big tires like they were 26" again.

I may not have a lot of experience with bike clutches, but I know that if you significantly lower your gearing you will make it MUCH easier on your clutch. Does this make sense?

 

[fast pom]

PS all the advice you will recive here is done with the best intent please dont think fellow GSers are trying to put you off , but a lot of us have made costly mistakes in the past .

 

[aaronbev79]

PS all the advice you will recive here is done with the best intent please dont think fellow GSers are trying to put you off , but a lot of us have made costly mistakes in the past .

I know, and I appreciate it. But there have been many guys who have used 750cc motors without a problem.

 

[salty_monk]

Thanks again, but if you do the math, 63hp with 800 lbs is a better power to weight ratio than 100hp with 1500lbs. The Rayvolution EVO -- the car that I am copying -- weighs just over 800 lbs and has a 750cc motor. Granted, my motor is not as good as a GSXR, but what I don't have in power I will try to make up some-what with gearing. And what I don't have otherwise, I will not worry about since I'm going to spend about $2000 total on this project since I'm building it myself.

How much do you spend on your Lotus cars? I bet I will spend a fraction and have a hell of a time with my cheap 750cc engine.

Ok, but you will want more power Lets now do the Torque figures for your 800lb (if you even get there, you'll be surprised how it adds up!) & we'll see a different story, Torque turns wheels. I'd be surprised if the 750 in the bike will pull much better than a 6 sec 60 time......

I think it's a great project & don't get me wrong you'll have fun whatever, I would just encourage you to "future proof" it in your design to take the bigger engine if possible.

The GSXR motor is a lot different to the one you plan to use...

Those replica's can be built & registered for $3000 or so depending on spec & how much you do yourself. As for those two.. about $4000.

The 750 is no different to any other GS engine. Very long lasting as long as it gets adequate cooling & plenty of oil changes.

 

[fast pom]

Then go for it my friend keep us informed on how you go like i say the 750 is a great engine all the best

 

[aaronbev79]

Ok, but you will want more power Lets now do the Torque figures for your 800lb (if you even get there, you'll be surprised how it adds up!) & we'll see a different story, Torque turns wheels. I'd be surprised if the 750 in the bike will pull much better than a 6 sec 60 time......

I think it's a great project & don't get me wrong you'll have fun whatever, I would just encourage you to "future proof" it in your design to take the bigger engine if possible.

The GSXR motor is a lot different to the one you plan to use...

Those replica's can be built & registered for $3000 or so depending on spec & how much you do yourself. As for those two.. about $4000.

The 750 is no different to any other GS engine. Very long lasting as long as it gets adequate cooling & plenty of oil changes.

Just to be clear -- this thread has never asked for help on HP or Torque -- I've asked for help on clutches and gearing. I'm well aware of where I am with power/torque, and I think it's quite obvious to anyone that a 1100cc engine is better than a 750cc engine. If you want to donate an 1100cc engine to my project, I'd gladly make a straight-up trade

Otherwise, I appreciate the kind concern, and I didn't mean to seem annoyed.

 

[aaronbev79]

Here are some pics of my actual bike, rear swingarm/6" wide wheel from ZX9R, and my seat. Also pictured is the Acewell 3900 custom gauge unit that I will be using to replace the stock GS750 gauges. The Acewell unit uses generic speed, RPM, and heat sensors so I will be able to run things without having to worry about extending the connectors as I would have if I were using the GS750 stock gauge cluster.

As far as gearing, I ran the numbers, and with a low profile tire on the 17" ZX9R wheel, a 46-47 tooth rear sprocket will put me around 95mph on the top end -- greatly reducing the stock gear ratio. Hopefully, this reduction, combined with upgrading the stock clutch, will keep this thing moving down the road. Are there any stock parts from an GS1100 that could be used on the GS750 clutch to improve it...such as the springs?

 

[fast pom]

Get your self a new set of HD Barrnet springs {not expensive] none of the clutch parts are interchangeable with the 750. Check the centre nut on the clutch hub is tight and that the basket is not groved were the plates sit. Like the acewell unit is the rev counter elec or dose it use the mec drive from the cam Thanks

 

[aaronbev79]

The Acewell uses an electrical signal for the tach.

 

[salty_monk]

I suspect the unit uses a magnetic pulse counter or proximity sensor to work out speed. You can mount them on a driveshaft or something similar, as long as you know what pulse ratio etc to put in there (for example 1 pulse for every turn of the rear wheel with a certain wheel circumference).
There's a few of these things out on the market now.... not sure on that one but the cheapest I've seen in the UK is about ?70 ($110). Not sure it comes with all the idiot lights like that one though!

Looking forward to following this project...