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Discussion Starter #1
Hi guys I am new to arctic chat but have been around old cats for a long time I have a few 79-81 5000 fa eltigres, I prefer them for there power to weight and simplicity, I appologise to the cat purists who cringe when they see what I have done to my vintage cats as they are slightly modified here is a pic of the latest one still needs paint I have all decals just cant paint until the off season. It has a 136" x 15" x 1.5" track, reverser chain case 40" ski stance upgraded clutches, It is a blast. It is swift runs 50mph in the snow and 85 on hard pack, nothing to be ashamed of for sure. But I have had this sled for years and have no idea of the hour or abuse that this ones engine has endured so I am planning on building an engine for it and Would like to speak with other fa piston port owners or engine builders who have experience with these motors I have a lot of high performance engine building experience but most of my experience relates to 4 strokes so any insite into how to make these things run would be appreciated.
 

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I have a good running 79. I had the crank pins welded and left the motor stock. It has Aaeen twin & pipes 38s. The best performance gain I did was from a late model A/C roller driven clutch.
 

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Hi, I was starting to wonder if I was the only free air eltigre guy who is looking for performance improvements, I am curious about the pipes and bigger carbs did you notice much improvement? How did it react to the improved flow and how did it effect the power band, I assume better top end but did it kill some of the low end torque?
 

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I was racing short snow ovals. I geared it down a few teeth also. As far as performance improvement I was quicker that a couple stock 5000s that ran with me. Before I did the carbs I remember at a vintage hill climb I was neck and neck with a mid 70s TX every heat. In the final I pulled the rubber boots off the air box and on that run I had him by 3 sled lengths. That told me it needed more air and fuel.
 

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Hi guy's. If your interested i have some insight on some mods for the 500 F/A. I have a '78 i have been speed running for a few years. Porting and smoothing the intake and exhaust ports helps with smooth fast air flow. I have twin 38 mm carbs. I have a custom made single tuned pipe. I have found that the twin tuned pipes are more finicky, and i make more power with the single. I had the heads shave .020 to boost the compression. Wiseco pistons that are balanced. I run VP C12 fuel with Klotz oil because i advanced the timing a coupe of degrees. I run a 102c clutch and run it to 9000 rpms. I run a reverse cam roller driven with a 1 3/8" belt. I converted the track to a rubber track and kept the 500 suspension with added idler wheels. I upped the size of the rear wheels and idlers to run the track 1/4" away from the slides. I dropped the suspension 1" by drilling out the holes in the front mounting bracket. The holes are there, just need to be drilled out. Now i have more track on the ground. I replaced the heavy steel ski's with Wahl's racing aluminum ski's. (Weight = HP)
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On the clutch pictures, the drive clutch in the picture is a 108c, and the driven has no windage covers. Now i have a 102C and the driven has windage covers on it.
 

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Discussion Starter #7
Awsome sled, this is exactly why I started this thread was to find out what others have done and what works, it seems bigger carbs are a must and 38 mics will feed it to 9000rpm thats awsome. I have several of these sleds and am going to assemble a "spare" engine, I am interested in the porting you have done, I have ported 4 strokes and was wondering on intake side smoothing the ports what are you finishing to, alot of the stuff I have done I finish to around 100 grit and exhaust/combustion chamber I polish, what about intake port height?, do you modify the height any to give it more duration or just to smooth airflow?, did you build the pipe? Looks like we are running similar clutch setups, however I am planning to swap to a p85 polaris clutch and try that. I have been thinking about racing one and would have to run a rubber track as cleats are pretty much banned what track are you running? Tub clearance is an issue so how tall is your track and how well does it hook. Thanks for replying to the thread.
 

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I smoothed the ports to 400 grit. As for raising the height, I probably did very little by polishing it, but make sure that you chamfer the opening enough so that the rings don't bite into them. A little strip of emery cloth 200 grit will clean them enough to take any sharp edge off, just don't chip the nicasil in the cylinder. The pipe is a custom made 500 cc single that was made to fit. (yes I built it). What venue are you going to race? Oval, drags, speed runs? They still run cleats in a lot of sanctions yet. If you do convert to rubber, I found a good used El tigre 6000 track and drivers. Any 116" x15, 252 pitch involute track will work depending on what type of racing you choose. You will need to change the drivers out also, that's why i found the track and drivers off the same machine so it was just a swap. By dropping the front of the suspension as i mentioned above, gained more clearance for studs. I should also mention, i dropped a size on my scissor idler wheels. (#33 in the image)
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Yes read that thread it had some good ideas in it, if I race it it would be vintage drags, I would have to check the rules on engine mods before I set it up to race. I have limited expierience with 2 strokes thats why I asked about grit finishes when porting. Did you use a program to design the pipe? I understand the theory on 2 stroke exhaust and could tig up a pipe but would not have a clue on chamber size and lengths to get the power band I want. Thanks for sharing your knowledge.
 

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I used a factory made 500 single and fabricated it to fit in the tiger. Doesn't really matter what brand, just find one that has approximate bends so it doesn't need too much cutting and welding. Running 660' or what ever distance you run will require gearing and a lot of testing. I run 1000' runs so gearing will be completely different. Also like in the write up, get rid of the plastic pads and spring in the chaincase. Buy a aftermarket chain roller and drill a hole to the bolt size in the kit, tap the hole for the bolt. I don't seal up the chaincase with oil, just use a couple of bolts to keep the cover on. That way you can change gears without a mess depending on track conditions. Just spray the chain like you would a motorcycle chain with chain lube and put the cover on. If you look at the first pic above, you will see a bolt sticking out of the chaincase. This is what i used. Sports Parts Inc. Chain Tensioner - SM-03093 Snowmobile | Dennis Kirk
 
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