Kawi2strokes.com Forum

Almost every H2 dragbike I have seen does not use the front motormounts ( some leave away the rear upper too).
Whats the reason? Just weight saving?
Has anyone tried this setup (leave away front brackets) in conjunction with rubber mounted engine?
Asking because my new "babe" has aftermarket drag-frame that does not have front brackets. Dont want to weld them on as frame is nice powdercoated......

On the other hand I want rubber mounted engine because:
- the (billet) engine is already like that
- I always had excellent expierience with rubbermounting. No frame crack in 80000 miles heavy motorway use....

Now a bit scared about too much engine moving using rubbermount with 3 mounts only and with heavy tuned engine .....

Any expirience anyone????

Ralf

PM Bill B he if anyone would know for sure.......

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

I have never run the upper front mounts, they transfer a lot of vibration to the chassis and for some odd reason the upper rear mounts will crack on some chassis if you use them. Take off the front mount and the rear mounts won't break. You CANNOT leave off the upper rear, the cases will distort and it won't shift gears. But I have never seen a rubber mounted drag engine, you may be in uncharted territory.

Didn't I read somewhere that the upper rear mount was left off on H1r and H2r's due to vibes back in the day?

Shifting a dragbike with an air shifter and approx 70 milliseconds kill time is much less positive than using your foot, also in drag racing a missed shift means you lose.

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"Patina" Derived from latin upaytina, definition: Too cheap to fix it

Thanks for clearing up Bill! If even the top-bikes like yours run with 3 mounts I should get no trouble with the frame.
The cases are very warp resistant and that rubbermounting is designed to allow a maximum movement of 1.5 mm radial and aprox. 1 mm axial. I'll give it a try .....

Or you could put solid slugs in instead of the bushes Ralf? Like on the rare few early H2B's that looked like they were planning for rubber mounting.

test-result:

it worked with rubber and 3 mounts so far.
BUT:
needed a chain adjustment every time after first 4 passes. After that it was okay. Seems the engine has found it's final position then.
Anyway I think this is not perfect. Will work to put the 4th mount on. A "clamp" solution might be easy to do....

No Hal, rigid mount is no option. Once you had rubbers you never go back! Not even for 9.x seconds

The H1R and H2R setups that did run the upper rear motor mounts were problematic at best, all the way down to not shifting, cracking the case boss right out, various other issues. What did evolve was a simple mount on the frame only, to hold the rear fairing stay rod.

Later H1R, and all real H2R used a different setup for engine mounting, Lord button mount inserts in the cases to handle side to side movement and reduce vibration. These mounts were inserted into the bolt boss ends on the cases, and then, they "bumped" against the sides of the motor mounts on the chassis. The engine was still held in place front to rear, up/down by the engine mount bolt to insert inner bore diameter. Tis setup was NOT at all like the GT750 full floater mounts in those engine/chassis setups.

On a lot of later road racers, I used a different setup. Upper rear mount was rubber isolated to the chassis IF I ran an upper re3ar mount, mostly I didn't. Front and front lower were rubber isolator mounted, so they would allow the engine to float in the chassis in a arc, up and down, and bushed the rear engine mount bosses, so it would allow the engine to pivot up and down on the rear lower engine mount structure. This kept the chain in good service/alignment/tension, but let the engine float in the chassis. Worked well, especially on a street bike setup.