siebenrock 1000cc conversion installed, suggestions for "what next?"

[DOINTHETON]

happy with the new found power increase, have a 32/11 rear end coming to get a little more top end leg. carbs next?- 40mm bings, mikunis, or? also thinking of norton peashooters for exhaust, like the look and sound. lastly a set of big valve heads? any suggestions or comments?

[RandyB]

http://garnet.acns.fsu.edu/~jroche/road_rod.html

Interesting read. I've talked to the guy. He's quite enthusiastic.

[28796]

happy with the new found power increase, have a 32/11 rear end coming to get a little more top end leg. carbs next?- 40mm bings, mikunis, or? also thinking of norton peashooters for exhaust, like the look and sound. lastly a set of big valve heads? any suggestions or comments?


I put the 1000cc kit on my 87 R80, kept the stock heads, installed 34mm Mikunis & the rear drive from the 88-92 R100RS/RT. Anything bigger then 36mm carbs is a waste of time with the small valve heads & just takes away from the amazing low end/mid range torque the kit gives the bike. Forget the Bings & get a pair of Miks or Dellortos so you can enjoy the immediate throttle response of a slide carb. For an exhaust I went with a full Epco twin crossover system w/ slash 6 style end caps on the mufflers.

[rinty]

If you're going to big valve heads, a set of 38 mm Mikuni flat slides would be nice. They would give you better throttle response than the Bings. The only disadvantage might be heavier throttle action than the stockers, which might be a factor for you if you go touring. My right hand was blistered every summer from touring on my stock RS, even after I had the whole cable system serviced.

I've looked at the Siebenrock catalogue, and their stuff looks exquisite.

Rinty

[28796]

All the Mikunis I've used have a much lighter throttle pull then the Bings so that shouldn't be an issue. With the big valve heads & large carbs most of your performance gain will be in the high end so take a look at the type of riding you enjoy most before proceding. Since I ride mostly on the backroads of New England having the low end/mid range punch that the small valves/carbs/kit gives you makes riding my bike a real hoot. I can lift the frt wheel well off the ground just by cracking the throttle open & it rips when I roll it on.

[DOINTHETON]

no bodywork, no mo' touring. the sole reason for buying this bike was price, low miles, and wanting to do this conversion.
most of my riding is upper rpm's. like to sprint and corner carve on these old airheads more than logging on the big miles. cafe looks and performance are my ultimate goals. 37/11 is turning 5500rpm at 90mph-ish, i only did this for a short burst since the converion is still new. seemed like it had plenty left but i had to resist the temptation to run it in the red just yet. i want the lower(numerically) gearing to keep the soccer mom's at bay on the highway.curious to just how much more "umph" potential lurks in this kit with the proper help.......
http://img.photobucket.com/albums/v224/billpack/HPIM1952.jpg

[28796]

Miks or Dellortos will make a nice difference. I ran the Bings initially before installing the Miks & the improvement in throttle response was noticble when I changed. You can open up your stock mufflers & improve the sound/performance abit without springing for new cans. 2-3 .5" holes punched or drilled through the diverter plate located about halfway through the muffler works well. I've run this set up on my R90/S for many years.

[vanzen]

re-work the heads.
that would be my first stage, given the other work you are dreaming of.
don't know the miles, but but get the valves right, now's the time to fit larger, if that's your mind – guides, seats, check springs, + gas flowing.

maximize what you got.

then worry about carbs and pipes and etc. – although unless you are building an exhaust that is "tuned" to the engine / riding needs, drilling the stock mufflers would likely be as effective as "peashooters".

AND: still depends entirely upon your expectations for the finished product.

AND YOUR BUDGET !!!!

[Isamemon]

that is one nice looking ride :doh

[Isamemon]

ok
looked a second time...........nice scooter

[GregFeeler]

that is one nice looking ride :doh


Yes, VERY nice! :thumb :thumb

[DOINTHETON]

thanks for the compliments. i like the look and color too.

the stock R80Rt heads that are on it, what can be done to them other than dual plugging to reap performance gains? what are stock valve sizes on an 83 R80RT, and can bigger valves be installed? any porting or performance valve job recommended? lighter weight components? this is a 9000 mile bike so i would like to work with the original, low mileage components as a basis.
thanks

[28796]

You won't see any real performance gains by dual plugging, if it's not pinging it's a waste of time & money. Mine runs fine on 91 octane with no pinging. With only 9000 miles you shouldn't need a valve job but its hard to say as some of the bikes left the factory needing one; at least in the late 80s. My bike had 33k on it & needed an exhaust valve (the reason I got it cheap) & a couple guides.
Stock gearing on mine was 32/10 which I found too low after installing the kit so I went to 33/11 which I'm very happy with.

[vanzen]

first get all components up to snuff.
bigger valves can be fitted.
your intakes, I believe, are 42mm. Older RSs used 44mm, 45s will "fit".
38mm to 40mm on the exhaust valves.
add in guides, clips, a 3-angle seat grinding and hand lapping.
maybe hi-lift (revised ratio) rocker arms or a performance cam?
conventional porting will increase flow 'CAPABILITY' @ 17%, with 7-10% HP gains.
adding material to the intake port to raise the port floor and a revised ceiling radius can provide additional flow and greater velocity.
how about straightening out those intake tracts? this improves both volume and velocity.
don't forget combustion chamber equalization – if not in harmony, a fight ensues.
head to piston matching is a good idea especially if aftermarket lightweight pistons are fitted.
or how about a 'long rod & short piston' combo?
if you up th CR, plan on dual plugging, maybe some work with cam timing.
of course, then you will want to enlarge the exhaust spigots to at least 40mm, or maybe even 45mm and do some flow bench testing to build an exhaust system tuned specifically to take advantage of all that fuel mix the engine will be sucking.
EVERY PART IN THE 247 CAN BENEFIT FROM GOING ON A DIET!
everything from the crank, rods, pistons, to lifter pushrods, rockers, & cam gear. everything.
can you say titanium?
and goes without saying, carbs to feed this hungry beast ...
OH! and did I mention a chassis stiff enough with real BRAKES that can handle all that !!!


– remember Fudd's 3rd law of thermo nuclear dynamics: what goes in must come out. or put another way: approach any performance modification as a 'package', or a 'system' or all will be for nought.


also remember: nothing is gained where nothing is lost

[DOINTHETON]

vansen,
now thats a list i can work with brother, let the games begin! regarding the heads, should i look into a big valve pair, or just work with my low mileage ones?

[28796]

vansen,
now thats a list i can work with brother, let the games begin! regarding the heads, should i look into a big valve pair, or just work with my low mileage ones?


Decide for yourself. What do you want? Low end/mid range torque or high end power? The beauty of the Siebenrock kit on an R80 is that it gives you all that point & squirt torque to play with. The bigger the carbs, valves, exhaust the more of that you lose.

[vanzen]

MY STRATEGY would be to OPTIMIZE what the Factory provided in a pre-emission euro-bike, something like this:
40 & 44mm valves. 40mm exhaust headers & drilled mufflers. 38mm slide carbs (Mikuni before Dellorto). NOT a 336 cam, but a better performing asymmetrical cam (as sold by Siebenrock) & a bronze front cam carrier. Match combustion chamber volumes, clean up intake ports, clean & polish exhaust ports. Modify airbox as per Snowbum's recs (http://pweb.jps.net/~snowbum/R80,%201980+,%20Airboxmods.htm) and a KN filter. Remove EPA plumbing. Omega crank mounted ignition, or at least a cam mounted version with a programmed advance curve vs a centrifugal one.
Balance crank and upper end, careful assembly with every bit measured and spec'd.
The result would be an engine with more power AT THE TOP, slightly less torque under 4,000rpm, still quite reliable, but puts the chassis at it's limits with good tires.

Oh, and make sure you got GOOOOD brakes!!!

Remember: bigger valves and the cam above improve top end hi-rpm performance. your valves + a 320 (torque) cam + 34-36mm slide carb + 38mm exhaust & a lot of the work / parts mentioned above would provide significant torque gains at mid range rpms – those used most on the street, and perhaps more beneficial!!

the difference defined in real terms:
option #1: Do you NEED to have a 130+mph capability?
option #2: Or will getting to 110mph RIGHT-NOW-QUICK suffice?

1st step: define your needs. be realistic.

[Pezz_gs]

vansen,
now thats a list i can work with brother, let the games begin! regarding the heads, should i look into a big valve pair, or just work with my low mileage ones?

I would leave the 38mm exhaust valves in.

The design of the head shows more beneficial gians available on the inlet tract.

I set up a set of R80 Heads with 44mm inlets 38 Exhaust and ported accordingly. Twin Plugged. Worked a treat.

Like Vanzen said, Once you have a sweet engine its the rest of the bike that needs work.

One thing I find amusing is guys who get the swingarm braced on a twin shock bike, but dont touch the rear subframe. 4 bolts carry the subframe which is also the top shock mount carrier. Might be worth looking at a cross brace 'X' between the top shock mounts and the top subframe mounts. You will lose your tool box.

So much to do and so little time . . . :thumb

Enjoy

Pezz:)