I got my 'combat scrambler' back on the road!

Discussion in 'Airheads' started by supershaft, Oct 17, 2012.

  1. Bluethumb

    Bluethumb Been here awhile

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    Regardless if you can pull 125 mph or 135, it's sounds like one fast bike. Would really like to hear what you did to build it up. Would you list in detail what you did? Motor, suspension, carbs, FD?

    And when are we going see a picture?
    #21
  2. supershaft

    supershaft because I can

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    Sure: The bike is a naked '92 R100RT with all the pollution crap removed and Staintune Sport mufflers.

    I started with a close ratio gear set. I swapped the intermediate shaft helical gear for the later pressure face angle and at the same time put a beefier input shaft and cush drive. The CR first gear got into the much larger cush drive so we had to machine it back down just a RCH. I kept the stock 33/11 FD. Love it!

    Then I put a sport cam in, titanium spring retainers, and cleaned up the ports a bit. Loved it. Big diff right off the bat. 32mm carbs stayed stock except for much leaner 262 needle jets. (Increased reversion really richened up idle and just off idle.)

    Then a friend gave me some 38mm PHM rubber mounted Dell's with no choke bodies. I filed about a third of the velocity stack threads off so the airbox snorlels fit right on the carbs like a 32mm Bing. Real clean looking IMO and it works! I started with R90S jetting and leaned it WAY out for a LOT more power. I disconnected the pumps and ended up with 130 mains among many other changes. All that got me around 30% more power from stock with great power all the way through the rev range to up above 8k rpm. Over the 32mm Bings, way more mostly midrange and top end. Not as big of a difference as just the cam but I love it!

    Then 70,000 miles later with 101,000 total, my exhaust guides were toasted. New guides. 42 to 44mm intake valves and a LOT of port work. My ports were badly mismatched. I took out a LOT of meat matching them up. Redid my intake valve to seat ID ratio by hand. Took .025 off the heads. Put new cylinders and 9.5:1 pistons in. (I had one compression ring groove wearing like they do so I sprung for all new.) New titanium retainers. Mine were hammered! Manton 4130 pushrods. Dual plugged it with the stock bean can and two .7 ohm Dyna's. Remapped the ignition curve from 6 to 32 degrees to 6 to 28. That's it engine wise. I have yet to do some airbox experiements with the new setup.

    Chassis: Fox twin clicker. Preloaded stock fork springs. Forks are on backwards. Headlight and handle bar windshield are frame mounted via a modified RT/RS front fairing/headlight mount. /6 style ignition switch. EBC organic pads. Steel braided brake line. K1 bars. San Jose top tree. A whole bunch of worthless IMO crap taken off including the side covers and their mounts. It's a whole big box worth of crap. That's about it. I will hopefully have some pictures in a month or so. I forgot to add that I cut weight by running a 19 amp battery too. I have better luck with them than the bigger batteries. They weight a lot less and they don't make your bike look like thay have a boat battery in them.
    #22
  3. DeutschMark

    DeutschMark Full Tilt Boogie

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    Shaft, I know you are a proponent of leaner and leaner mains, but that didn't work in my case with Mikunis and twin-plugs. Different bike, carbs, etc., but going to 195's from 170's got me four more mph on the top end and I had to back off.

    I started at 150's then moved my way up. The 160's would rev cleanly to redline buy I'd get a surge (only on a cold day, was absent when 80 degrees) when backing off from WOT as flow transitioned to the richer needle/needle jet. I went up 2 sizes to 170 and thought all seemed well. After discussing my jetting with someone who is very familiar with Mikuni/Airhead setups, I plugged in my 195's and instantly noticed more power. I still have some more testing to do with some other mains, but I'm running out of good weather here in MI.

    Buy or borrow a cheap handheld GPS to get an instant and reliable reading so you don't have to rely on radar guns and charts.
    #23
  4. supershaft

    supershaft because I can

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    Not if you read between the lines. What I am a proponent of is running them as lean as you can versus as rich as you can. There is a lot of hp free for the taking between the two setups. The way my bike was set up, it ran fine with 155's in it but it ran WAY better with 130's. I have seen the same thing play out at shop dyno days time after time on all sorts of bikes. Like I have always warned about, most of it has to do with port velocity. Higher velocity, smaller jets. Whether or not your bike is a big port of a small port makes a big diff. So does the airbox setup. The airbox setup really effects just off idle jetting. Now that I raised my compression from 8.5:1 to a guestimated 10.0:1, put bigger intake valves in, and really hogged out my ports, I might see bigger mains in my future. I have got to tune on my new setup some yet. Airbox setups that use to just kill my midrange now barely effect it. I am going to test freer flowing airbox setups and exhuast and see what happens. Even if I end up running 170 mains with my new set up, I bet it would sound just as good minus three or four (or five!) hp with 190's in it. Typically speaking, that is the nature of jetting. THAT is what I am a proponent of! :freaky
    #24
  5. Uncle Pollo

    Uncle Pollo Long timer

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    Super is uknowingly guiding me into tunning happiness. I
    #25
  6. supershaft

    supershaft because I can

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    I really do hope I am helping somebody. Yes, sometimes things do start off too lean on the mains (setups very often start off too lean just off idle but that is another story) but most of the time it's the other way around. So many peole think of jetting as putting the biggest jets in there that will still work. Wrong! It's all about putting the smallest jets in there that still work. If your butt dyno can't tell the difference a real one will!
    #26
  7. Uncle Pollo

    Uncle Pollo Long timer

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    i was too lwan on main but too fat on the pilot and nj
    changed the needle and upped the main and got better but a big hiccup
    went down 2 steps on nj and back to the 6f4 and rides better.

    in a couple days i will step back to 140 main and see

    my riding is from 5000 to 10000 feet so i have to ride on the lean side of things

    if i was going down i would tune on the rich side

    i love being able to deccide a change, visualize it, predict the outcome, and be right!
    #27
  8. supershaft

    supershaft because I can

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    Something about my Dell's that I forgot: If they are too rich just off idle they surge. I am running a few tuning experiments. I think I am making ground. I am going to run it like I have it know for a while and see what I think. The jetting is all the same but I am now running 165 mains all because of airbox mods. Basically no airbox top and I shortened my velocity stacks by about three inches. It just barely effects my low rpm power versus killing it before the port work and higher CR. Now it is pulling a lot stronger at 8k rpm. The intake is noisy now! My valves definitely are not floating with those pushrods which are almost three times as heavy as the stock ones but that is what the big money pushrod guys are doing so I am giving it a try. Does it help? I don't know other than it has to be helping a least just a bit since those stock rods flex a lot. I do know that it is running good as it is! I am still running stock springs with no preload. I was thinking about preloading them just a bit but my stack height was already a bit short according to spec so I didn't. I don't think it is hurting me at all. In my experience, more spring pressure takes a lot of longevity out of the setup so I try to not go there.
    #28
  9. supershaft

    supershaft because I can

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    My shortened rubber velocity stacks are coming loose. Rats! I can't figure a good way to do it. First off I am going to go back to stock length and make sure it is worth the trouble (I think they will be but I am not absolutely sure just yet) and then I am going to find some aluminum tubing to machine on for the snorkel/box junction and clamp some after market ones on the inside of the box. I will probably end up with about the exact setup that was on a race bike I worked on that RAN. My bike is semi regularly lifting the front wheel at around 5k rpm in first with no bumps or anything but smooth pavement involved. I think that is around 45mph! I have raised the compression on enough bikes to think that a lot of my performance gains are from my port work. I was a bit worried because they where so far mismatched I took a lot of meat out matching them up. I usually follow Smokey's advise and leave the port floor pretty much alone but I had one raised floor a lot higher than the other so I took the high one down and matched them up. I raised the roof a lot on the other to match that up but that almost always works. That and the top sides. That always works too if you do it right. Same story all over again with the exhausts minus the top sides of the exhaust are just like the bottom sides.
    #29
  10. supershaft

    supershaft because I can

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    Well, now that I have my airbox setup dialed in, I am going to recheck some even bigger mains and some K2 jet needles. I think it might need to be richer up above 7k rpm and not any richer down lower. K2's are thicker all the way down from my K9's I am running now. A couple of more tests and then I will be set up!

    My poor landlord thinks his CRF450 is going to out run my airhead now that he has it geared to go 100mph. When he had it geared to go 85, he could barely out pull me until I shifted to second at around 65mph (meanwhile he had gone through at least three gears) and then I would leave him behind (as far as the engines are concerned!). He had five gears inside of two of mine. Now its three since I shift into fourth around 105. Now I am going to smoke him from the get go! :lol3
    #30
  11. Rucksta

    Rucksta SS Blowhard

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    Gee Whizz SS can't you find someone your own size to pick on :D
    A stock R80 will outrun a CRF450.
    Tell him to get a real bike.
    #31
  12. supershaft

    supershaft because I can

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    A stock R80? Quite a bit less less hp. A little more torque and right around twice the weight. I don't think so. But I know what you are saying. If you saw the roads we ride on, you would understand that, besides his now big power defecit, his total package is a huge advantage. He knows that much as well as I do but why he thinks taller gearing will enable him to out motor my now much stronger running engine? I don't know either!
    #32
  13. supershaft

    supershaft because I can

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    Well, I am almost done jetting my bike. I don't know how Rob conducted his airfilter experiments that showed him that his flat filter restricted airflow above 5700rpm. I just did some test runs and with my setup and there is virtually no difference up to 8000rpm with or without my K+N. My setup: Stacks shortened to just inside the box and then I did my test hill with JUST the K+N filter on top of the box and then with no filter. Virtually no difference. Does the K+N flow much better than the stock paper? In my experience not that much if any. Yes, you can see through a K+N but they keep my square airbox cleaner by far than the stock paper filters or anything else I have seen used. That's why I run them. Squeaky clean airbox. Stock paper? At least a bunch of dust gets in!
    #33
  14. disston

    disston ShadeTreeExpert

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    Wow ! That's great SS. You're just in time for the Winter riding season. :freaky
    #34
  15. supershaft

    supershaft because I can

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    I know. I just got home. First the Dirt Bag Challenge and then an awesome jazz show. Talk about two different worlds!! It was a cold ride home. I now have my jetting pretty much sorted out until I weld up some new exhaust. Earleir today I cruised to the next block from the Challenge and got into the throttle from around 30mph. Even though I was leaning into it way over the bars the front end still came up a foot until I let off of it. No bumps or anything. Just another honest straight up power wheelie. I have ridden other airheads that would power wheelie in first but they didn't have a CR gearset with a 33/11 FD! Yee ha!
    #35
  16. RGregor

    RGregor Been here awhile

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    Now, I don't want to depress you, but I know beemers that will do power wheelies in second gear.
    Mine for example (stock gearset, also 11/33 FD).

    Welcome to the club ...

    However, power of your bike at high revs seems to be very impressive. Keep on posting.
    #36
  17. Airhead Wrangler

    Airhead Wrangler Long timer

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    Keep in mind though that he's using the close ratio racing transmission which has a pretty tall first gear.
    #37
  18. RGregor

    RGregor Been here awhile

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    I'm totally aware of that fact and I know the ratios of the CR gearset.
    #38
  19. supershaft

    supershaft because I can

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    Well, I am just happy with how my bike is running and trying to share info. I will hopefuly get pictures soon but right now I have some important trips and whatnot to take and then hip surgery at the end of the month so I am afraid it won't be soon enough. I am afraid that the pictures aren't going to say much since it's pretty much a sleeper.
    #39
  20. ME 109

    ME 109 Long timer

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    The only way we'll see a piccy is to send the paparazzi around.:D
    #40