Grant's trail
Member
New project, 175 twin powered SL90 I'm going to make it look like a 70 though. I dont know how It will turn out but will post pic's as I go....
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"Were going to need a bigger shoehorn!!"
- Thread starter Grant's trail
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New project, 175 twin powered SL90 I'm going to make it look like a 70 though. I dont know how It will turn out but will post pic's as I go....
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M
MATT
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I cant wait to see it when its finished.....thats really gonna piss off the neighbours
Grant's trail
Member
I saw the u-tube video and the old guy even older then me on it.lol Yea the motor needs lots of polish also needs comp. in one cyl. but it was cheap. right now I'm mocking it up Mon. I cut out some of the frame to raise the eng. about a 1.25 to get the sprocket more in line with the swing arm piviot. I fabed up a new plate to fill in the space I needed for the head to fit. when I get a little farther I'll put up some more pics. I think these engines were about 18 horse or so so for now were going to build it back stock and see how this thing works. Im thinking 12" wheels low profile tires, a xr80 front end. and I dont know yet about the battery or fuel tank yet just one step at a time.
CB175s were good for the high side of 80mph, "back in the day". Judging by your pix, you should realize a sizeable forward weight shift - exactly what I'd want, for overall balance. Since that also carries a significant weight increase, you might do better to source fork legs from a larger/heavier bike than an XR80. As for wheel size, if you're looking for improvements at higher road speeds, then overall tire diameter matters more than wheel size. On a CT70, it's tough going much larger than a 60" circumference tire, or about 19" overall height. On the other hand, if you're going to build a custom ST90, the larger frame allows for larger tires, simplifying suspension setup and improving high-speed stability in one shot.
Grant's trail
Member
This was animal week, Heres some pic's making room for the Head and raising the eng to get the sprocket closer to the swingarm piviot. I look at that u-tube ct 175 and he has his eng a little further forward then I'm shooting for. I do think the extra weight up front will help the balance, and Racer's idea of bigger forks might be something I will look into when I see how much weight this adds. anyway here's some cutting and fab pic's. Also look at how heavy duty the gusset is that suports the stearing head on this SL90 frame is compared to a CT frame. also it looks a little thicker but I haven't cut a ct frame to know for sure.
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Grant's trail
Member
Thanks Bill, First I have to get the eng to fit, Then I'll probely have to cut up a new steel tank or more then likely make one out of alum. I'm thinking about maybe finding a smaller battery, then I would have more room for a little bigger gas tank . I'm going to try to keep the electric starter. Who knows maybe it will have small sattle bags with a battery in one side, and the electrics in the other. Also the 175 has a mount on top of the rocker cover I'm going to weld in a new mount there and that will tie the eng into the frame and use the engine as a stressed member of the frame.
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Grant you want me to get you some specs on the pinstipe size?? LOL
Great job on the fabrication of that engine mount, top notch!
Grant's Trail said:
CT70 frame thickness is greater than you might think. In terms of the total quantity of steel used, there's more in a CT than a Z50. By all indications, the CT70 frame is stronger than the more conventional Z50 frame - both overall and lb-for-lb. It's the result of cross-sectional area, like a driveshaft, and compound curves + the two welded ribs formed by the R+L stampings...unibody construction applied to bike frames. The same applies to the CL90 & ST90. Such frames are not always easy to modify with predictable results. Even a relatively small change can upset the balance/break the structural chain.
Nice TIG work & metalfinishing. However, you've removed a convex, curved, section + center rib and replaced it with a concave, rectangular-section, piece. IMO, there's no argument that the frame has been weakened. No idea as to the real-world implications; it may still be more than strong enough, as it sits. Adding a stressed member forward of the newly-added engine cutout is a damn good idea. A second, aft of the engine cutout, forming a triangle tied-into the engine or engine mount area is even better.
As for front suspension, shorter tires result in higher velocities when dealing with the same road surface unevenness. With the heavier motor, the finished bike is likely to tip the scales a lot closer to SL175 weight than CT70. In other words, the front suspension will have to absorb harder "hits" than it would on a bike with 24" tall tires. FWIW, I'd be researching fork legs originally used on 125-250cc models, that are slightly heavier than your finished project.
Grant's trail
Member
I'm still trying to decide on the color...something to go with Brians flame's (Brian do be carefull when you peal them off please!! lmao!) If I have enough room I might add a second top mount to the frame right before it was notched out, maybe off the back headbolts, also the engine has two lower mounts but I do want to make sure the upper part of the frame doesn't flex, or if you do a little wheelie (I Do mean LITTLE lol) it wont be a problem for the notch that will clear the head. I have an extra set of forks off a XR100 or XR125 I don't know for sure I think there 32mm legs If they were shortened a little they might be better for the added weight, I'll try to post up a pic of them and maybe somebody can tell me what there off of. Thanks everbody for the Ideas!