1976 Nitro Grass Drag Set Ups

[midniterupper]

Wow Clint! That would be very helpful! I think I could install a total of 4 wheels/brackets on my slides. If you send me 4, I should me all set then. Could you use any American parts? I have parts from the two I bought earlier. One of them has a really neat cylinder head temperature gauge that I've never seen before. I'm sure we can work something out for them.

My email is [e-mail] or you can call my cell at 248 420-4863 and we can exchange information then. Thanks again Clint, we definitely have to get together one of these days. I would love to head off to the races with you and your car.

Take care now, we'll chat soon.
-Paul

[Ruppsforever]

There are some brackets that put the wheel further down into the track. They are for running on grass. The ones that came with the sleds place the wheels even with the hyfax. Let me see if I have some too. Pretty sure I do.

[mrrupp1]

Paul, this is my cell number 303-909-0240, I will give a call this weekend and we can work out all the details. Clint

[mrrupp1]

The ones I have are the brackets they called marginal snow kit. It seemed like the wheels always stuck below the slider, even if the hyfax were new. Let me know if you still want them. Rupp used a 5 inch wheel, I think the bracket would still work if you put bigger bogey in there. I'm pretty sure you can get an 5 1/8 inch diameter bogey may work just right. Let me know. Clint

[Ruppsforever]

Clint those are the ones. I thought they were for grass racing. I can't seem to find any different part number for them in my books.

[midniterupper]

Yes Clint, I would love to install those on my sled! I had no idea that Rupp even considered manufacturing a kit for marginal snow conditions, that was way before Global Warming. The resourcefulness and engineering of Rupp is still amazing even after all these years.
Do you know if they had a placement pattern for their wheels or just replace the existing brackets? I guess wheel diameter would play into the overall effectiveness too.

I will focus on getting the new gears and chain in to see what this 19/35 combo is all about. We should be able to test with your wheels right away. I think 71 mph is right around the corner. Nothing else has even come close to that speed but I believe we can attain it. Nothing more effective than a good spanking!
We'll discuss the strategy as progress continues.

Clint, we can chat more later when you have time. Thanks again!
-Paul

[mrrupp1]

Hi Josh, those are the only brackets that I have ever seen on the Rupps I have ever owned. I normally take them out . The reason I take them out is because the bogey breaks off the bracket and breaks lugs off my drive sprocket. We don’t run on the roads or the lake very often so we really don’t need them. Most of our riding is in the powder. Take care. Clint

[Ruppsforever]

I have 12 of these brackets. Paul you want to put these wheels where there is the most friction. The worst friction is probably right where the bend in the slide is. If I were to grass race I would have wheels to keep whole track off the slides. You can drill holes in the slide rails to put them wherever you want them. I bought these when I had intentions on grass racing but then I never got into it.

[midniterupper]

Hi Josh, thanks for sharing your expertise! I believe you are right in having the wheels located at the lower bend of the rails and along the length as well to reduce the rolling resistance, and probably the more the better.

The set of hyfax I have on the sled now has quite a bit of wear on them (new last fall) which I guess is to be expected considering the lack of lube and dirt they are exposed to. It shows there must be substantial pressure on them. I'm kinda thinking this wear right now may be to our advantage if we add the marginal snow brackets and wheels because the hyfax should be tucked up out of the way. Still there for support if needed but no longer riding only the hyfax surface. I'm excited about this, never thought about just drilling additional holes where needed. Much easier than turning out offset brackets!

I am not sure exactly how many wheels I ought to add, do you think the additional wheels will consume more horsepower? These bearings seem to spin easy enough and can't imagine they would take much.

I'm working with Clint right now on some wheels and brackets that he has on hand. We'll see how they match up for offsets and additional clearance and I will keep you updated. If you could hang on to your set up until I get a chance to fit Clint's, I would greatly appreciate it. I think he is sending some out this week so I should be able to try them out when they arrive. I'll be sure to let you know asap. Sure appreciate your support Josh.

Now that I have you on the line sort of, I am noticing a developing a glitch that I would like to speak with you about if you don't mind.
In my last few test passes, right around the 450' mark, the sled is like hitting the brakes very shortly. It's noticeable when I ride it like I hit the brakes real hard, real quick. I lose 500 rpm then it comes right back like it never left off. It seems to happen around 7900 rpm. My wife video records each pass but you can't hear it or see it. However, on the radar gun, it'll show I'm climbing to 67,68 then it drops to 66 mph and stays there.

The plugs look nice, not lean and the max exhaust temps are recorded at 1120/1085. Do you think I could be briefly emptying the carb float bowls? Have you installed a higher output fuel pump? I'm thinking fuel at this point but I'm really not sure. She runs great and strong in every other way. It just started doing this since I started hitting 8,000 rpm in testing. Any advice would be very helpful.

I still have to change my gearing and test it then to see if it's still there so I'll keep you posted for sure.
Well, I'd better run along now. Lots to do this time of year!
Thanks again,
-Paul

[Ruppsforever]

I don't think your running out of gas. Could be your slides are sticking. If your hyfax is wore a bunch normal bogie brackets would work for you too. The minimal snow brackets drop the wheels like 3/8 to 1/2 inch. But if your hyfax are wore a lot regular ones will take the track off of them too.

[mutt]

Really no need for a higher out put fuel pump. In theory supports 115 hp. Mikuni round has no trouble with Polairs trail triples pushing 135 hp in real world. If your doing back to back runs in the summer I would consider getting the pump away from the crank case in case your vapor locking

[midniterupper]

Hey, Thanks guys! I just wasn't sure about my fuel situation. I have never had an issue with the Mikuni round fuel pump delivery before and I did rebuild the pump during the winter. I will verify the float levels are correct just to be sure.

I gotta get busy on the sled and change the gears, maybe the problem will chase me there which could be and issue with the multi angle helix. One thing at a time right?

Thanks again to all for your input and expertise, I feel I should have you all autograph the hood!
Until the next time, enjoy life!
-Paul

[midniterupper]

Good Evening Fellow Ruppers,
Been busy the last few days but did a get chance to do some testing with the new 19/35 gearing. No improvement on top speed using the same last set up. The sled feels faster right out of the hole through mid way, hooks up nice, lifts the skis a couple of inches off the ground for the first 15-20 feet.

Then the sled feels "flat" like it's going through the motions but really not gaining much more pull. I tried two previous set ups that had both worked well but there was not much difference in testing with them this time. Same speed, back down to 63 mph.
The rpm's are also down to around 7400-7500 so I'm thinking the motor is being more loaded down with the lower gear ratio. I have a 49 degree helix (verses 53 degree) to install to maybe lighten the load and increase the rpm.

I still need to try the Aaen purple primary spring too. So far the Polaris Almond/Gold is hitting the hardest out of the hole. I did install the new set of Comet A-25 that came notched. So far, it looks like the engagement is pushing 6500 rpm. We will see how that works out.

Had to stop testing earlier today due to the high winds. We have two very large, very old wild cherry trees that are next to the shut down area. The trees were creaking and swaying pretty bad so we will have to take them down right away. We have some great weather coming for the next week so hopefully we will get more time in.

We are gaining I'm sure, just have to figure things out with the new gears. Not really too surprising isn't it?

Chat soon,
-Paul

[Ruppsforever]

I would definitely try the 49 or even less than that. I always used the stock secondary but ground my own angles on them. I liked 38/35 multi angle.

[midniterupper]

I agree Ruppsforever, the 53 degree is pretty steep. It helped get us up to 63-66 mph but I can't seem to squeeze any more than that out of it. Today we did a little more testing, still hard to dedicate the time to doing it right now. This is the time of year on the farm to get at those projects!

Anyway, the testing today went rather well. Fooled around more with secondary springs and the winner is still the Arctic white. The secondary stays amazingly cool with that spring, and we still always get 1 mph more with any set up on the primary. We are installing the straight 49 degree for the next round.

Okay, now for the primary. I installed the Comet A-25 notched arms today, not sure how I like them though. With the Polaris almond/gold spring, the clutch is engaging at 6700 rpm! I like them high but this may be a bit much, almost impossible to bump the sled to the starting line and getting around. Max rpm is at 7700 so it's only 1000 rpm of usable range. Launches hard when it does engage, tops out steadily at 7700 and stays there. 65 mph every time and feels like it's still pulling. I believe the 19/35 gearing is a great combination. I think we can still get more top end out of it, just finding the right set up.

Just for kicks and giggles, I'll install Olav's purple spring he sent out to try with the notched A-25 arms, maybe a little lower engagement will occur without sacrificing top speed. At least now we have some data to compare it with.

Overall, it was a good day of testing, got more notes from every pass to review later. The exhaust temps are still low, they didn't seem to be greatly affected by the main jetting changes like they should. I was going more lean to bump them up but the temps didn't change much and I started to develop that little bog so I went back up two sizes. No more bog and attained higher top speeds but I sure don't understand why the temps are so low (1080/890 degrees). I think I will swap out the exhaust probes to see if there is a difference in the two temp readings. Maybe we have a bad probe somehow. Then I may put them back and try swapping the carbs left to right and notice any change. Confusing for sure. With the smaller jetting, the plugs did look more lean. Installed the two sizes up and we are back to looking nice. Just so cold that I'm not sure we are really burning 100%.

That's about it for now, Thanks again Ruppsforever for your advice. When I get this month's pension check it's back to Mickey's salvage yard to see what other helixes are available. You'll have to share how you custom make your own helixes, your combinations sound very interesting!

Until next time, keep Ruppin' up!
-Paul

[Ruppsforever]

I made a few helixes but I had someone else make most of them for me. I had a friend of mine offer some advise so I did what he said. You take JB weld and fill up the voids where the helix angle is. I had a shit pile of different angle helixes made at all different angles, and several multi angle ones made too. I'm anxious to hear what the 49 degree helix does. Do you have a piston light ?? That takes all the guess work out of the pipe temp. I always shot for 1/4 " of piston wash. Maybe a little less. Once I found my jetting was perfect in the piston then I looked at what my EGT was. If that varied with weather changes jetting changes needed to be done. But even after the changes were made I always checked piston wash.

[midniterupper]

Cool Josh, great information! I never considered using JB Weld to build up the helix material. That stuff is amazing, works in many applications. Total Flow used it in adding material on the ports on the Top Fuel heads, easy to blend and it holds up well.

Regarding the piston wash concept, are you talking about the combustion pattern on top of the piston? I don't have a good light or inspection camera but I would like to have one on hand, do you have a favorite that you use? I believe that would be a great visual indicator of what's actually happening in the holes once I learn how to interpret it. Always so much more to learn.....

I did do some testing yesterday, got some interesting results. I switched the two exhaust temp leads just to see if we may have a bad probe but the readings remained the same, both cold on the mag side. About 200 degrees colder than the pto side. I have an idea it may be the oem silencers getting plugged as they are rattling once again. So today I removed them for the next testing session, hopefully tomorrow.

I installed the Aaen purple spring in the primary to see how that performs overall. Also installed the 49 degree helix during testing.
With the A-25 arms the engagement kicked in at 6500, topping out at 7700 rpm. Best top speed with that combination was only 64 mph so not the best but worth noting.

On the next test I installed the Polaris 10MW arms as they have always been consistent, usually topping out around 63-64 mph. Didn't change anything else other than the arms and we dropped down to 57mph. Engagement is low at 5000 rpm so I needed to tuck grind a little more off the heel (just did that for the next time we try them). Max rpm was 7500 climbing up to 7700 so apparently the 49 degree helix is helping the rpm toward the end of the run. Same rpm pattern as the A-25 arms just not to high engagement. 7 mph slower though, kinda weird isn't it?

So for tomorrow's test run I installed the A-2 arms @ 48.8 grams again and removed the silencers. Still going to continue to experiment with the 49 degree helix to see if we can get any advantage over the 53 degree. If it looks promising we'll go get a 47, 45 degree and hopefully a 48/44 to play with.

I am running out of ideas for trying different primary arms. It seems the sled likes the 48 gram weights at least in respect to actual weight, it always goes faster with more. I looked through the Aaen clutching book and see that Comet offers quite a few selections of weights around the 49-50 gram range. Maybe try something in that area just to see....

I did receive Clint's marginal snow wheels and brackets yesterday, I will wait until I get the sled testing procedures done first as-is so I keep things consistent and well documented but I am excited to try them out. So many good things yet to do!

Well that's the latest for now, we'll stay at it. Our first race is going to be at Nelson's Snow Motion in August. Can't Wait!!!
Thanks again Josh for your help.
Until the next time,
-Paul

[midniterupper]

Whew! Hot one today in Northern Michigan. Was able to make 1 test pass this morning. I'm sure my distant neighbors must have wondered about hearing a rabbied mosquito on steroids as I removed the silencers to make this test. I did so to verify the exhaust temp difference thinking we may have a clogged silencer.

I also removed the 10MW weights as with this current set up, they really slowed things down using these weights for some reason. I installed the A-2 arms for this testing, last pass with the 10MW's topped out at only 57 mph, this pass with the A-2's went up to 64 mph again. RPM pattern was (6000 rpm engagement) then immediately to 7400 climbing steadily to 7800 and stayed there. I believe the sled is liking a shallower helix angle as the rpms stay up there and actually climbs where we want it to be so we are going in the right direction there. We'll pick up more helixes to play with later this month.

The exhaust temps did improve gaining 49 degrees on the pto (was 1065 degrees) and 137 degrees (was 851 degrees) on the mag side. Sounded really cool too! So tonight I just completely swapped carbs from side to side. I included the slides, fuel lines and choke cables to stay with each carb respectively so it should reflect some interesting observations.

No other changes so it will be simple to keep track of.

Let you know more tomorrow,
-Paul

[Ruppsforever]

Very interesting stuff. Anxious to hear how the carb swap does. Been there done that. Sounds like you are on the right track !! The best piston light I have found is the Stylus Reach Streamlight. Super bright !! Easy to see piston wash. I think they are like $30.00. One more thing to take into consideration is more MPH doesn't mean you are getting to 500' quicker. Wish you had a timing system of some sort. Also if you reach a dead end throw a new belt on it. New belts can be pretty sporty if yours is wore.

[midniterupper]

Hey thanks Josh for your tip! I did purchase a little extend a light today and used it to look at the top of the pistons and also through the exhaust ports too. Everything looks great.

I am investigating a few timing systems right now, looking at the Polaris Timing Console, the Brower TC Timing system, the Race QP Timer 3000 system, the AIM Technologies Mychron5-2T system and finally the Turbo Dynamics Performance Meter & GPS Speed Gauge system. They all look helpful, we will see..

One test pass today. This test was to see if the cold exhaust temps follow the carb swap and they did. So I reset my float levels to .600" instead of the .650" that I had them set at before. Maybe I'm flooding out the cylinder somehow. I'm leaving everything else the same for the next test to see if the temps even out.

The good news is the sled stayed consistent between passes from yesterday to today. Topped out at 63 on both days and the shift characteristics stayed the same too.

I should be able to install the marginal snow kit that Clint sent over this weekend hopefully, I'm sure it's gonna help out. I think we are about ready to begin experimenting with the fuels soon too.

I am wondering if anyone has tried out the Thundershift arms in a 440? They have a kit that has a range of 36-50 grams and they have the 3 hole locations to tailor your shift pattern. They're not that expensive considering how many other clutch arm combinations you could go through. Curious if they work on these engines?

That's it for now, we'll chat again soon. Thanks again for your interest!
-Paul