Engine Mounting

[BusaTransplant]

So for those of you not familiar with my project, I’m swapping the engine from a Hayabusa into a 1980 GS850 frame. Now is where I need some input from the people with some build or swap experience. I need to know the most lean angle I can get away with forward or backward on the engine without drowning the crank in oil or starving it of oil, and I know it’s probably not ideal for proper fuel atomization but I’m looking for a boot between the intake side of the head to the throttle bodies that runs at a 45° because of space constraints. And information, expertise, or constructive ideas are appreciated! (Also to note in the pics the back of the frame is lifted an inch or two so the tank isn’t sitting on the TB’s and I need to get the back of the engine sitting closer to the swingarm pivot for a better route for the chain to avoid any mechanical interference, these are just initial mock-ups to dial the placement in)

 

[sixpack577]

FWIW
I love wheelies, and I can ride them past 11 o'clock, nearly vertical, and for miles at a time.
I put over 17k miles on my gen2, as well as alot of miles on a friend's gen1 and my B-king.
Countless wheelies, and Never Any issues with the engine, the Busa engine doesn't starve for oil at all, because if it did...I would've found out.
(SV650 or ZX11 and it's another story, they Will starve for oil).

You may need to do some cutting and fab to make the engine fit properly, and you really need to weld in some frame gussets or supports anyway, which may help to reshape around clearance problem areas.

 

[BusaTransplant]

FWIW
I love wheelies, and I can ride them past 11 o'clock, nearly vertical, and for miles at a time.
I put over 17k miles on my gen2, as well as alot of miles on a friend's gen1 and my B-king.
Countless wheelies, and Never Any issues with the engine, the Busa engine doesn't starve for oil at all, because if it did...I would've found out.
(SV650 or ZX11 and it's another story, they Will starve for oil).

You may need to do some cutting and fab to make the engine fit properly, and you really need to weld in some frame gussets or supports anyway, which may help to reshape around clearance problem areas.

Do you have any good pictures of the chain routing on a Busa? My biggest clearance concern is the pivot point on the swing arm during suspension travel. And my concern with the orientation of the engine is if I tip it too far forward when mounting it and end up just whipping the oil all the time.

 

[sixpack577]

Do you have any good pictures of the chain routing on a Busa? My biggest clearance concern is the pivot point on the swing arm during suspension travel. And my concern with the orientation of the engine is if I tip it too far forward when mounting it and end up just whipping the oil all the time.

Sorry, I don't have any pictures of the chain.
I wouldn't be concerned about rotating the engine forward a couple degrees either, but nothing dramatic.

 

[BusaTransplant]

Sorry, I don't have any pictures of the chain.
I wouldn't be concerned about rotating the engine forward a couple degrees either, but nothing dramatic.

If you have a chance to snap a couple pics from the front and back to see the chain’s path when you have the time I’d appreciate it.

 

[sixpack577]

If you have a chance to snap a couple pics from the front and back to see the chain’s path when you have the time I’d appreciate it.

I don't have my gen2 anymore.
I ride a gsxr1k now.

 

[pashnit]

Front and back of the chain's path

 

[pashnit]

 

[sixpack577]

I think he needs pictures from directly behind, over and under.
Where the swingarm visibly mounts to the frame.

 

[BusaTransplant]

View attachment 1645003

View attachment 1645004

View attachment 1645005

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Very clean and that helps, thank you!

 

[BusaTransplant]

Rear mounts are set, welds are ugly but good enough for placement. Once motor is dropped back out they’ll be cleaned up. I think I got the sprockets in a pretty good line to where I won’t get interference with anything. Will def test more before doing front mounts.

 

[Bumblebee]

View attachment 1645038
Rear mounts are set, welds are ugly but good enough for placement. Once motor is dropped back out they’ll be cleaned up. I think I got the sprockets in a pretty good line to where I won’t get interference with anything. Will def test more before doing front mounts.

You ae very dedicated to your hobby-I'll give you that....

 

[sixpack577]

View attachment 1645038
Rear mounts are set, welds are ugly but good enough for placement. Once motor is dropped back out they’ll be cleaned up. I think I got the sprockets in a pretty good line to where I won’t get interference with anything. Will def test more before doing front mounts.

Looks really low.
How much ground clearance will be below the headers?

 

[BusaTransplant]

Looks really low.
How much ground clearance will be below the headers?

That’s soon to be next on the list to figure out I can compensate for some ground clearance when I set my rear suspension, don’t think I can get anymore height out of the busa fork though?

 

[sixpack577]

That’s soon to be next on the list to figure out I can compensate for some ground clearance when I set my rear suspension, don’t think I can get anymore height out of the busa fork though?

No more heigth from the forks, they are what they are.
The engine needs to come up higher in the frame, otherwise your gonna put flat spots on the bottom of the header tubes when going over bumps...and it's always the bumps that you Don't see that get you.
So long as you have chain clearance under the front of the swingarm, you can raise the engine a couple inches, or add a roller and/or relife cut there.

 

[Bumblebee]

No more heigth from the forks, they are what they are.
The engine needs to come up higher in the frame, otherwise your gonna put flat spots on the bottom of the header tubes when going over bumps...and it's always the bumps that you Don't see that get you.
So long as you have chain clearance under the front of the swingarm, you can raise the engine a couple inches, or add a roller and/or relife cut there.

To add to this, the lean angle would be at such a degree, you'd barely get around any corners...if this bike will be used to only straight run drag races you might be ok...

 

[BusaTransplant]

No more heigth from the forks, they are what they are.
The engine needs to come up higher in the frame, otherwise your gonna put flat spots on the bottom of the header tubes when going over bumps...and it's always the bumps that you Don't see that get you.
So long as you have chain clearance under the front of the swingarm, you can raise the engine a couple inches, or add a roller and/or relife cut there.

Unfortunately once I set the tank all the way down I don’t have anymore room to go up. So might have to get creative again.

 

[sixpack577]

No room for the throttlebodies at that angle with the tank at that height either.

 

[BusaTransplant]

No room for the throttlebodies at that angle with the tank at that height either.

I’m looking to see if I can find a short 45° boot to fit the throttle bodies(I know it will probably make the atomization of the fuel less then factory but I’m just looking for a solution.

 

[sixpack577]

I think someone already mentioned it before, but maybe make the stock GS tank a dummy, and mount a fuel cell under the seat.
You could cut the top of the frame and the bottom of the tank out, and the tank would basically be a shell with no bottom, and room for the tb's.