Need help with custom intake!

[850 Combat]

Well, not really (305 vs. 350). The 350 was a marvel of its day. The 360 ushered in some improvements and manufacturing simplifications, but never achieved the overall reliability until evolving into the 400 series.

Not that it matters, it really wasn't much evolution from the 350/360 to the 400/450. Buzzy 180 degree crank uncounterbalanced no power two valve to 360 degree crank 3 valve counterbalanced twin which was as quick as the two strokes. The 400 shares the spelling of the manufacturer's name with the earlier motor pretty much.

I've read that the 360 was less successful than the 350. Can't remember why. The only real difference I can think of is the 6 speed it needed because Yamaha and Suzuki had one.

I say go for it as far as the build goes. There are plenty of those old bikes around anyhow. A log style manifold might work and be relatively easy to build.

A guy I know put a Turbo Honda 550 in a TX500 frame. It had nitrous bottles hidden in fake mufflers on each side. The Exhaust went over the head. It made no sense, but he wanted to do it, and he did it.

[razor02097]

There is the fact of a very large motor in a very small frame is just inherintly dangerous, but in a seriously awesome way.

Just like motorcycling itself. We all have to be some shade of idiot to get out on what is functionally an engine with wheels, blasting down the highway at seventy miles per hour with nothing between us and the world to keep us safe.

But the joy of the experience is well worth the risk, and so it's okay that we're all a bit of an idiot for being in this hobby.

I didn't mean it insultingly, more in the way that they call some truly radical hot rods "Daft" or "looney" or "crazy" and so forth.

I apologize in advance and I don't usually do this...but I have to completely disagree.


A rider doesn't have to have a shred of idiocy to ride a motorcycle. The idiocy of a rider is described as a motorcyclist decides Not to use any protective gear, perform risky maneuvers, showing off, speeding and/or general reckless behavior.

When I ride I dawn padded gear, boots, gloves and a full face DOT and Snell approved helmet. I may not have a metal cage around me but I have metal, carbon fiber, lexen and synthetic materials. I may not have air bags but I do have massive amounts of padding to help prevent injury. Yes a car might be safer in most situations but no matter what you are in short of a tank you are suitable to injury during a serious accident.


It is because I enjoy riding a motorcycle and enjoy the benefits like fuel economy, motorcycle parking and the great communities that the motorcycle brings...not because of idiocy.

[AJ]

Don't know why the link to the Triumph manifold didn't work, but here's a photo. It's something like a "log manifold" like 850 Combat suggested.

[AJ]

Not sure what to make of everyones talk of "idiot." If it makes you all sleep better at night, I do have a background in mechanical engineering and this isn't my first project.

If I wanted a supermoto I would simply ride my KTM instead of doing this. I'm curious why everyone thinks this frame is such a bad choice. Is it because it is physically small compared to the frame the engine came out of? Is it because I cut away so much of the back bone? Please share.

I'm not trying to be smart ass. I just figured if people have an issue with what I'm doing it would be good to discuss it (in a civilized manner) since someone may have something to say that has slipped my mind.

That is pretty much why I'm doing this. How many people would ever consider this? Now how many of those people would actually follow through with the idea? I'm hoping this will be a true one of a kind bike when I'm done.

It's fun how this thread is evolving... going from "What the f**? This is crazy!" to actually trying to think creatively about how to pull this beasty off. RG, I think you've handled the criticism pretty well.

Back to the technical, I had not noticed how you had cut the back bone of the frame to shoehorn in the engine, but now see you've really gone to town with it. How much clearance do you have to brace that, especially because the tank tunnel is already tight? Are you planning to form a tube around it somehow? You'll need to close the bottom of the box for stiffness.

Also, will you be able to get your cam cover off for valve adjustments? And where the h@ll are the coils going to go? (ok, those are small fry questions, but inquiring minds want to know! )

[AJ]

Not that it matters, it really wasn't much evolution from the 350/360 to the 400/450. Buzzy 180 degree crank uncounterbalanced no power two valve to 360 degree crank 3 valve counterbalanced twin which was as quick as the two strokes. The 400 shares the spelling of the manufacturer's name with the earlier motor pretty much.

I've read that the 360 was less successful than the 350. Can't remember why. The only real difference I can think of is the 6 speed it needed because Yamaha and Suzuki had one.

To my eye, the biggest changes were the cam and the transmission to 6 speed. The 350 used external blocks to hold the cam bearings, and these blocks were slid into the ends of the heads. The 360 used a much more modern design with the cam bearings directly in the head, eliminating a ton of precision machining. They also massively simplified the cam chain tensioner. For the record, I think I have built about ten CB350 engines, with no. 11 in my garage awaiting for me to finish this GS1100e that continues to frustrate me.

I also don't know recall why the 360 engine was not reliable, as I had already moved into 4 cylinder bikes by the time the 360 was out. I did piece together a 360 out of parts for my girlfriend/future wife to get her around campus. That was totaled after she was hit by a car, and I moved her onto a GS450, which was lightyears ahead of either the CB twins.

[Dave8338]

I've got a 360 Honda engine sitting on the shelf in the shop. As for weight, that thing is a REAL PIG ! ! ! I'm not concerned for the strength of the frame. It will flex a little. Keep in mind that the single back bone and down tube is larger in diameter than the twin tubes of the GS bikes. Braced correctly and tied back tight to the engine, you can create a whole new stress member, the engine, that Suzuki never did.

Yamaha pulled it off in the Virago series of bikes. Worked GREAT.

Inverted forks in the plan?

[AJ]

I've got a 360 Honda engine sitting on the shelf in the shop. As for weight, that thing is a REAL PIG ! ! ! I'm not concerned for the strength of the frame. It will flex a little. Keep in mind that the single back bone and down tube is larger in diameter than the twin tubes of the GS bikes. Braced correctly and tied back tight to the engine, you can create a whole new stress member, the engine, that Suzuki never did.

Yamaha pulled it off in the Virago series of bikes. Worked GREAT.

Inverted forks in the plan?

Don't know about the 360, but the 350 frame also tied to the cam cover with a pair of triangular brackets. I suspect this was done for stiffness.

[Racing Geek]

What kind of KTM do you have? I wanted a 525 and ended up getting a DRZ400E with a street title. Still dream about the KTMs though.

It's a '98 KTM 400RXC. It's an older bike but it's still a blast to ride. This pic was before it went into street mode. The Camaro behind it was another project.

I've read that the 360 was less successful than the 350. Can't remember why. The only real difference I can think of is the 6 speed it needed because Yamaha and Suzuki had one.

To my eye, the biggest changes were the cam and the transmission to 6 speed. The 350 used external blocks to hold the cam bearings, and these blocks were slid into the ends of the heads. The 360 used a much more modern design with the cam bearings directly in the head, eliminating a ton of precision machining. They also massively simplified the cam chain tensioner. For the record, I think I have built about ten CB350 engines, with no. 11 in my garage awaiting for me to finish this GS1100e that continues to frustrate me.

I also don't know recall why the 360 engine was not reliable, as I had already moved into 4 cylinder bikes by the time the 360 was out. I did piece together a 360 out of parts for my girlfriend/future wife to get her around campus. That was totaled after she was hit by a car, and I moved her onto a GS450, which was lightyears ahead of either the CB twins.

I've also read that the oiling at the top of the motor wasn't as good as the CB350 and that's why there were never many people that raced them.

Don't know why the link to the Triumph manifold didn't work, but here's a photo. It's something like a "log manifold" like 850 Combat suggested.

I suppose that one could work if the spacing is right. The S&S one I have looks more like the picture below which is why I mentioned needing really sharp turns for it to work. I wonder if that older Harley manifold you posted about would have the same or similar port sizes as the GS? Hmm...

It's fun how this thread is evolving... going from "What the f**? This is crazy!" to actually trying to think creatively about how to pull this beasty off. RG, I think you've handled the criticism pretty well.

Back to the technical, I had not noticed how you had cut the back bone of the frame to shoehorn in the engine, but now see you've really gone to town with it. How much clearance do you have to brace that, especially because the tank tunnel is already tight? Are you planning to form a tube around it somehow? You'll need to close the bottom of the box for stiffness.

Also, will you be able to get your cam cover off for valve adjustments? And where the h@ll are the coils going to go? (ok, those are small fry questions, but inquiring minds want to know! )

In the photo showing the top of the motor, the two holes you see along the edge of the cut is where the stock upper motor mounts where fro the 360 engine.

The tank will be custom so I'll have as much room in the tunnel as I want. I do plan to close off the bottom of the tube with some plate and I'll be adding a brace like this. The bar used for mock up is 1" conduit. The coils will be placed on the inside of the brace underneath where the gas tank would go. If you where to kneel down next to the bike you could probably see them poking out under the tank but they should otherwise be out of sight. Note that the front part of the brace will be a tighter curve then what is picture. I couldn't get it any tighter without severely crimping the tube.




This is all the metal except the backbone pieces I cut off of the frame. Plasma cutters are wonderful!



I will be using all the GS engine motor mounts (2 in back, 1 on bottom, 1 in front) and I'll be make the breather on top into a motor mount to further brace the back bone. I'll be adding a brace going directly between the upper shock mounts to better support the shocks and give me something sturdy to sit on. I'll also be using some plate steel to gusset the frame in a few areas.

I will not be able to remove the cam cover for a valve adjustment unless I totally redo the backbone or I live with having to remove the engine every time the valves need adjustment. I've decided I would rather remove the engine every time since I shouldn't have to remove it very often.

I've got a 360 Honda engine sitting on the shelf in the shop. As for weight, that thing is a REAL PIG ! ! ! I'm not concerned for the strength of the frame. It will flex a little. Keep in mind that the single back bone and down tube is larger in diameter than the twin tubes of the GS bikes. Braced correctly and tied back tight to the engine, you can create a whole new stress member, the engine, that Suzuki never did.

Yamaha pulled it off in the Virago series of bikes. Worked GREAT.

Inverted forks in the plan?

Yes, the stock 360 engine is a pig. That's why I think the 350# wet weight is actually a little generous of an estimate.

Since the F2 forks have been recently rebuilt with stiffer springs I plan to leave them alone. If I ever run across a RS125 front end or something similar, I would consider swapping the F2 forks for that. That opens up all kinds of issues with what I have currently so it would have to be a pretty good deal though.

[boontonmike]

That car was my first car. Mine was an 86 Iroc-Z in white. I miss that thing. Looks like we have quite a bit of tastes in common. Nice Ktm by the way, looks real clean. I would love to see the street wheels on it too.

Looks like you are on the right track with the frame modding so far. This may be a case of jumping to conclusions, because it looks like you know whats going on. I have a little faith in this.

[Racing Geek]

That car was my first car. Mine was an 86 Iroc-Z in white. I miss that thing. Looks like we have quite a bit of tastes in common. Nice Ktm by the way, looks real clean. I would love to see the street wheels on it too.

Looks like you are on the right track with the frame modding so far. This may be a case of jumping to conclusions, because it looks like you know whats going on. I have a little faith in this.

Mine is an 87 IROC-Z. A lot of chassis (braces galore), suspension (Koni shocks and adjustable everything), brake work (Corvette), and obviously the wheels are Corvette (18x10.5 with 295 rubber front and back). It will be for sale in the Spring.



The KTM won't be taken out until we get a good rain to wash the salt away and there is room in the garage. Is there a "post pics of your other rides" thread? I'll put some more pics of past/present vehicles in there.

[AJ]

That car was my first car. Mine was an 86 Iroc-Z in white. .

You guys are making me nostalgic. My first car was a 1972 Challenger with the 340. Cream with a vinyl top. Sold it when gas hit 50 cents a gallon, since she was good for maybe 14 mpg if I drove like a grandma. Given how much that Challenger has appreciated, it would have more than paid for the wasted gas! Suspect those IROCs are still pretty cheap as collectables. Looks like the trans ams are finally starting to move.

[850 Combat]

Mine is an 87 IROC-Z. A lot of chassis (braces galore), suspension (Koni shocks and adjustable everything), brake work (Corvette), and obviously the wheels are Corvette (18x10.5 with 295 rubber front and back). It will be for sale in the Spring.



The KTM won't be taken out until we get a good rain to wash the salt away and there is room in the garage. Is there a "post pics of your other rides" thread? I'll put some more pics of past/present vehicles in there.

those were stout autocrossers in their day. I never owned one, but traded off with a guy who had one for a number of dollar runs. Very strong acceleration out of slow turns, I thought. Of course, all those mods, except the shocks, would have been illegal in F Stock...

[boontonmike]

She's pretty. I'm lovin the hardtop with the charcoal rims. I bet she handles nice with all the bracing. I miss how well my iroc turned even with stock suspension. I've been debating getting another one in the next couple of years, I work at PST now so I can get parts at a great price. My ideal combo would be a hardtop 3.1 v6, add a turbo, t56 trans, 4.10 posi and every brace along with some bilsteins and mild lowering springs.

Ah the thoughts seeing your car brings up, haha.

[Racing Geek]

You guys are making me nostalgic. My first car was a 1972 Challenger with the 340. Cream with a vinyl top. Sold it when gas hit 50 cents a gallon, since she was good for maybe 14 mpg if I drove like a grandma. Given how much that Challenger has appreciated, it would have more than paid for the wasted gas! Suspect those IROCs are still pretty cheap as collectables. Looks like the trans ams are finally starting to move.

My Camaro averages 14mpg city, 22mpg highway, and will sometimes drop below 10mpg on race day.

those were stout autocrossers in their day. I never owned one, but traded off with a guy who had one for a number of dollar runs. Very strong acceleration out of slow turns, I thought. Of course, all those mods, except the shocks, would have been illegal in F Stock...

I autocross it but built it with track days at Road America as the end goal. For autocross I'm put in S-Mod but I use a street tire index since I don't have the money to spend on race rubber every year. There is plenty of torque even with the stock motor. So much so that I even made an adjustable rear sway bar to make it easier to figure out the best setup.

She's pretty. I'm lovin the hardtop with the charcoal rims. I bet she handles nice with all the bracing. I miss how well my iroc turned even with stock suspension. I've been debating getting another one in the next couple of years, I work at PST now so I can get parts at a great price. My ideal combo would be a hardtop 3.1 v6, add a turbo, t56 trans, 4.10 posi and every brace along with some bilsteins and mild lowering springs.

Ah the thoughts seeing your car brings up, haha.

Over 1g on street tires when I had it on a "skidpad" (aka big flat parking lot).

I'm trying to sell the car to fund my motorcycle hobby and to start putting money aside for my next car project. Here is a quick rundown of that...
-- V10 (~500hp/500trq)
-- 6 speed manual
-- AWD
-- 1930's (ish) sedan body
-- 350/xx/17 tires at all corners
-- spartan interior
-- estimated total weight ~2600#
-- estimated total cost ~$15,000
I have sketches and parts already modeled in Solidworks and Inventor. I just need the time, money, and space to do it. Pretty much everything is figured out.



To get back on topic here is the build thread that I started.

http://www.thegsresources.com/_forum/showthread.php?p=1582719&posted=1#post1582719

[AJ]

Any more thoughts on the manifold?