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Post by mrrupp1 on Nov 5, 2019 16:27:54 GMT -6
It sounds like your getting her dialed in. It great to see somebody racing a liquid Rupp. They are my favorite of all Rupps. I have give or take 60 and 20 of them are liquids. You get her to turn 8000 and you be the talk of the track. Good luck. Clint
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Post by midniterupper on Nov 5, 2019 17:01:21 GMT -6
Thanks Bud, Your input and assistance is a great contribution too. I've always loved to see the Rupp Nitros racing, great sound, futuristic features and we just don't see many of them around the tracks here in Michigan, a lot of Yammies though. It will be nice to bring it out with it running so nicely (even tho it's not quite there yet) and kick butt at the track. I'm sure no one is expecting it to do much, same old gang always seem to win so it's gonna be fun! My wife has been running the radar at the finish line, she can't believe how much better it sounds (and the reading she gets!)
Thanks again!
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Post by Ruppsforever on Nov 5, 2019 20:16:51 GMT -6
Sounds like you are on the right track !! Stock gearing on the 440 is 19/35 but I wouldn't play with that right now. That will change everything you are doing. Perhaps you're cutaways , pilots and needles are way different than stock. When you are done racing this weekend check this all out. Stock is 230 mains, 50 pilots, 1.5 cutaways. And the other stuff I can't think of at this time. When checking engine timing you have to rev motor past 6000 rpm to make sure timing advances. All my sleds the clutch engages at 7500 rpm so that is basically free wheeling too. I would put money on it that you are turning 8000 rpms right now. Don't worry what the tach is saying to you. After the races you will have a lot of time to check things over. Don't break it before you race it.
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Post by Ruppsforever on Nov 5, 2019 20:22:01 GMT -6
It sounds like the carbs that came with the sled aren’t the originals. I would make sure they are 38s. It seems like they run the best with 38 mikuni in stock form. On my stock motors my main jets are 190 both cylinders 50 on the pilots and 1.5 cut out on the round slides. On the needle it seems they like the one that came stock in the 76s I can’t remember the number off hand. I live in Colorado and we race around 8 to 10000 feet in elevation so we do have to lean them down. And that’s with running an air box. Ruppsforever knows way more then I do so I definitely listen to him over me. One more thing I’m running 19 top 39 bottom for gearing. Good luck racing. Clint [/quo Clint I know a lot of stuff but so do you !! Josh |
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Post by midniterupper on Nov 6, 2019 6:30:33 GMT -6
Excellent advice! I will leave everything alone for now, it's running so well. Looking forward to this weekend's appearance (and performance!), it's gonna be fun. I've learned a lot from you guys, you all have helped me out more that I could ever expect so thanks again for your input. I must be happier because my wife is happier and its all because the sled is happier, very cool!
One thing I did do to the motor that I forgot about is I did stuff the crank while I had the engine torn down. Maybe that is affecting my main jetting selection? Not sure on that but for next year I would like to install a racpak with EGT & RPM. I think that would help determine the jetting a little easier, and maybe a digital signal would be more accurate than my old VDO.
I have made some shim plates for the front mount on the rear suspension. When I had the suspension out of it, I studied those plates and made a few matching the angle and dimensions of the two originals that the sled came with. I am looking to lighten up the front end by using these plates but I don't know if I am on the right track. Have you guys fooled with weight distribution on these sleds? The front end of this sled will not even raise the skis on take off, and the witness marks left on the track after a pass appear to be gouging the ground with ski pressure. Always trying to reduce friction...
I will keep you all posted on this weekend's results. So exciting, thanks again!
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Post by mrrupp1 on Nov 6, 2019 20:52:33 GMT -6
The way Rupp says you can put more weight on the track and less weight on the skis is put the thick end of the shim to the front of the sled. They say you can use two on each side. It does work I’ve done it many times. Josh tanks for the compliment that means a lot coming from you. But your sleds have kicked some a$$ I brag to my brand x friends all the time . Midniterupper good luck this weekend run straight and fast. Be safe. Clint
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Post by midniterupper on Nov 7, 2019 5:47:29 GMT -6
Thank you for your research regarding the suspension shim plates, I understand their function way better now. I will proudly represent the Rupp racing community by giving it my best, will let you know how we do when we get home Saturday night. Thanks again to everyone!
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Post by midniterupper on Nov 7, 2019 18:10:09 GMT -6
Welp, the snowmobile club hosting the drags this weekend just sent out a facebook post announcing the races are officially cancelled due to water and 8" of snow/mud at the starting line. Bummer! That means I now have until September 2020 to try all kind of things, should be even faster by then!
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Post by mrrupp1 on Nov 8, 2019 17:38:55 GMT -6
Well that's a bummer. Have a great winter can't wait to here from you next year. Clint
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Post by midniterupper on Nov 9, 2019 8:29:00 GMT -6
Thanks Clint! I think we may try our hand at ice racing this year. The sled is running awesome and we already have snow here. There is a track to our north called the Mancelona Motorplex that has a nice set up for racing. I think we need to go (my wife says she can't tolerate me waiting until fall!).
Thanks again for all your help and advice, looking forward to dialing her in, we're so close. I still have lots of things to try, never have verified timing on it yet. Would like to see what fuels can do. Maybe send you the motor for you to massage? This is really getting fun!
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Post by mrrupp1 on Nov 11, 2019 11:46:56 GMT -6
That sounds great, the man you need to help you with your engine is Kevin Hasse at Pipestone small engines. He knows the Xenoah inside and out, plus he has everything for them. Here is his number 1-269-461-6421. The one you should talk to about drag racing on the ice is ruppsforever his sled kick butt. Keep me posted. Clint
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Post by nitrofa340 on Nov 11, 2019 23:09:09 GMT -6
Heres a bone if you ever want to try the stock hex clutch. 294 ramps cut for 5300 engagement, stock green primary spring, 105 weights, 19/39 gears, cut your stock secondary helix to a straight 34 degrees or a 36/34 combination & use a red Polaris secondary spring with 13 lbs tension on the secondary. Also dont over look the suspension. If you can find them, use the curved F/A suspension leaf springs for maximum ski lift/weight transfer. Add as many wheels to the rails as you can get under there. This combination will get you into the high 60s mph in 500 ft. I ran 65 mph in 350 ft at the grass drag radar run race that Rick aka Snosnake put on back in 2011 with that combination. We also won the Ladies "C" Stock Shootout class at the Princeton race the same year with the same set up. Another bit of advice, use your radar gun or timing system to determine gains/losses, dont rely/trust on your tach for tuning. The only thing your tach is good for is launching the sled off the start line.  |
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Post by midniterupper on Nov 12, 2019 6:02:22 GMT -6
Wow! Thanks guys for all the help and guidance with this sled, your expertise and wisdom from over the years sure proves itself. I'm writing a journal to keep track of all the tips and pointers, it's all been so very helpful and encouraging. I am really looking forward to further testing, the sled just keeps on improving. I agree with testing using other than stock gages, I have been using a VDO extreme analog tach that I mounted on the sled (the stock one doesn't work at all) and we've been using a Bushnell Velocity radar gun for verifying my speed.
I have been purchasing most of my parts from Kevin at Pipestone, he has been very helpful. I will see if I can swing by his shop sometime soon, he's about 3 hours away. It would be well worth the time to get schooled! I love the idea of reducing the rolling resistance and lighten up the front end, seems like a lot of ski pressure for a 404# sled. I believe there is speed to be gained in that area.
The rpm's recorded on the tach is very consistent: if the tach is right, the engagement rpm right now is 4700 to bump the sled forward and the funny thing is the max rpm seems to always stay right at 7500-7600 tops. It's almost like a mechanical rev limiter. She's perky, no bog or hesitation on the stand or on the ground, just won't climb any higher. I do have another VDO I can put on though I'm thinking of putting on a racepak to get my egt's and a digital readout for the tach. Going down the track, the sled speed takes off rather slowly but then about 150' into it she really begins to wake up and pick up the pace but at the 500' line I'm out of distance it seems. Top speed with the radar gun has only been 66 mph but it's a lot better than when we started! I believe the sled has great potential, just need to dig it out. We're gaining on them for sure.
The vintage sleds that we race against around here are almost all Yamahas, some Polaris triples. I find that some of the yammie boys are installing the old Viking 540cc fan cooled engines in the 440 chassis. They are quick but only topping out around 67 mph so they are within reach. Same with the Polar boys, even with their triples. A modded out 1977 SRX is producing around 90 hp, those seem to be about the fastest, nice light sleds. Our Xenoah motors are producing 87 hp stock. With a little tweaking I think the Rupp ought to be a very difficult sled to beat. Slowly we're getting there, step by step......
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Post by nitrofa340 on Nov 12, 2019 6:25:10 GMT -6
Another thing to check is your cdi box. Make sure it is a true '76-78 box and not a box from a '73 model sled. Even though the '73 box looks identical to the '76 box and will make the engine start and run decent the timing curves are very different. You will never get 8300 rpm out of a '73 cdi box. Been there done that. Look at the number stamped on the cdi box. If I am remembering right the '73 for the Tohatsu engines starts with a "2" and the '76 Xenoah box starts with a "5".
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Post by midniterupper on Nov 12, 2019 15:00:55 GMT -6
Excellent, I will take a look at it to see which version it has. I bought the sled back in 2009 at the A-1 Show & swap meet here in Michigan. The sled was together but did not run. Sorta sold "as is, condition unknown". The guy selling it didn't know much about it, I was just glad to get it as a project. I finally found time this year to put it back together, found a cracked piston skirt and many other problems but one by one they've been eliminated and repaired. It's been a blast to somewhat restore it and get her running so well now. Still has quite a ways to go yet, but holy cow! What a sled for drag racing vintage! A lot of fun, a lot to learn. I began riding snowmobiles in the Upper Peninsula in 1969 when I was 10 years old. I remember when the Nitro 400 was every kid's envy, hanging out at the local dealer after school studying every detail about the sled. Now I'm 60 and can't believe this is my most important sled! We used to race our skidoo's in the stock 700 & 800 class with MSDRA back in the late 90s's and we missed it terribly. Grass dragging fell apart for a while in Michigan but now it's gaining popularity again. Vintage racing is perfect for us now. I'm compiling a performance log of things that we've tried for our Nitro along with the results to sorta track everything from where we started. I also made a list of ideas and suggestions to try from the great folks on this forum, all of them help and are greatly appreciated. I would love to make this 440 a serious threat to the foreign based competition. The races we go to are mostly just local snowmobile club it based through out the state. The tech inspects are not very technical, primarily safety checks. I found the stock vintage classes here are not truly stock, more a compilation of more recent technologies. My Nitro is now leaning in that direction (tho nothing can't be undone!) by utilizing the P-85 primary and the reverse secondary. Anything to help make her fly! We still want to keep everything friendly and fun with no hard feelings, but it's always the same clan of guys and same manufacturer of sleds that seem to win sequentially. We didn't start off this way but it's fun to watch them squirm now, they're beginning to get nervous. Can't wait!  |
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Post by Ruppsforever on Nov 12, 2019 19:16:21 GMT -6
Nice of you to stop by Dale !! How the hell you been ?? Midniterupper if these are the clutches that you are going to stick with pick up some more weights and springs for the primary and get some different helixes and springs for the secondary. I have always used a Comet 102-C with the stock secondary with different helixes I had made. Always make sure you listen to Dale. I learned so much from him over the years. Just like his last couple of posts I learned a few more things already.
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Post by mrrupp1 on Nov 12, 2019 21:35:43 GMT -6
Midniterupper you have the two best Rupp drag racer there are helping you now. I’m going to sit back and read and learn myself. I can’t wait to here how you do on the ice. Good luck. Clint
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Post by nitrofa340 on Nov 13, 2019 6:54:11 GMT -6
Nice of you to stop by Dale !! How the hell you been ?? Midniterupper if these are the clutches that you are going to stick with pick up some more weights and springs for the primary and get some different helixes and springs for the secondary. I have always used a Comet 102-C with the stock secondary with different helixes I had made. Always make sure you listen to Dale. I learned so much from him over the years. Just like his last couple of posts I learned a few more things already. Hey Josh how have you been? Long time since we talked. Call me any time. My phone number is still the same. Thanks for the nice compliments. I have a lot of respect for you as well. We will have to talk & catch up soon. |
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Post by midniterupper on Nov 13, 2019 6:56:30 GMT -6
Boy, this is really cool! I believe we have the sharpest minds on the planet helping out with this one, Fantastic! What a wealth of resources and talent eh? I am humbled by the great support you all have been offering, not only to me but to the rest of the Rupp community and racers that follow your posts of wisdom! You guys are the best, I'm overwhelmed by your willingness to help get this sled to the absolute best of it's potential. Thank you so much, wow!
I am so excited about the ideas and input from you guys, makes it difficult to shut off my mind at night to get some rest! I have kept all the original parts that came with the sled in a box so I don't lose them. I think I will try basically two drive systems: the OEM secondary, spring & helix along with the Comet primary that it had. I have a lot of springs and weights that I've already tried with that so there is potential there. I also have the P-85 primary that I bought from a local sled salvage yard and of course the Arctic reverse secondary. It appears there is a lot of springs/weights to experiment with there too.
I think I will take another look at the sled to find out some information you all have mentioned, especially the cdi unit. I'll bring it back in the shop today and get things started.
One thing I do want to offer to this community for all your assistance and help is that I have a small machine shop here with a pretty good size lathe (15x50) and of course a Bridgeport mill along with a variety of welders. If any of you good folks need something machined up for your projects, please give me a hollar. I'm sure I can help out. I just have conventional machines but my son has a CNC available to us as well. The machines have come in handy so far, I used the lather extensively for making the new 4 wheel rear axle and for trueing up all the idlers getting rid of the high spots and reducing rolling resistance. So they're here if you guys need them, I would be more than glad to return all the favors!
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Post by nitrofa340 on Nov 13, 2019 7:27:48 GMT -6
By the way you guys are giving me way too much credit. Much of what I learned about making a stock liquid Rupp run hard came from John Holinshead up in Canada. The guy was a wealth of ideas/experience/information. I was just fortunate to meet many great racers over the years that steered me in the right direction. And just smart enough to listen.
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