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

[GQROD]

http://www.gearingcommander.com


This is the gearing calculator i used it's good because it goes up to six speed transmissions for ratios.

Hope it helps.

[aaronbev79]

Hi mate i race a GS750 good tough engine as mentioned before my only concern may be the clutch there not a bad unit but you are very limeted on the up grades as compared to the 1000 .
All the best with your build

Yeah -- the clutch is certainly my primary concern. However, I'm hoping that lowering the gear ratio will help that quite a bit. Improving my low end should make it much easier for the motor to move the additional weight. However, I figure if I do both -- lower my gearing AND improve my clutch -- that I should be fine...but we'll see.

[salty_monk]

If you can get one.. I would put a 1000 or an 1100 Engine in. Why start at 750? You'll get bored with it pretty quick..... I know that from my Lotus 7 replica's.. you always want more power.

[aaronbev79]

If you can get one.. I would put a 1000 or an 1100 Engine in. Why start at 750? You'll get bored with it pretty quick..... I know that from my Lotus 7 replica's.. you always want more power.

Well, I've spent more time looking for a reasonably priced engine than anything else with this project. And if there's one things that's true, 1000cc and bigger engines are WAY too expensive compared to 750cc motors. They are used in sprint cars, Locost projects, kits cars, and nearly anything else -- so they go for way too much. Plus, I was really wanting an entire bike because I needed one with a title (for licensing purposes), complete engine, wiring harness, gauges, and frame. At that point, I might as well purchase an entire bike. And finding a 1000cc or bigger bike that's complete and running well is not going to happen for anything near $300 -- I've tried.

I've spent months and months searching craigslist, local junkyards for bikes, ebay, and local classifieds and the GS750 was by far the best deal available. I don't have a lot of money to spend on this project, so I am trying to get the most out of what I have.

As far as power, I've talked with a lot of guys who have used 750cc bikes and they are more than happy with their results. 63hp on a car that weighs 700lbs, and is geared properly, will be more than enough for what I want to do.

Besides, I've already purchased the bike for cheap, and I'm sticking with it for now. If after it's built I am really wanting more, then I will drop in a bigger motor when I have more funds, but for now I am more than pleased with having a GS750.

What I really need are creative ideas for making the GS750 something that will work for this project.

[fast pom]

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,

[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

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

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