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Discussion Starter · #1 ·
Just got the motor out. Approximately 180 hrs on this stock motor. Going to take her to CT for a new build 540, +1 head, Carb. Not sure if I’m going to upgrade Cam yet (has 8/06). Was looking at RE in Tucson first but they have gone through some changes (John retired and sold the business) and they said they wouldn’t be able to get to it for months. Talked to Allen and he said bring her in. Can’t wait to run her next dune season.

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Oh boy! Anxious to hear a ride report. I've got a ton of hours on my stock RFS head and a scarred 525 cylinder that's begging for some work and an overbore.

Dad's factory 540 kitted machine with a 806 cam and stock head feels a little flat on the very top. Even being fed with a 43.5mm carb. My gut tells me the intake valve size and cam are probably holding it back. It runs and pulls so well in the sand everywhere else we don't feel it's worth it to mess with it and make it worse somewhere else. Maybe when it's ready for a rebuild someday.... He's kind of a lugger so bottom end to upper mid range is where he likes to ride it. When I ride it in the dunes I don't notice any drawbacks either. Only when I get on a harder surface like a track do I notice it signing off on the top a bit in the overrev. I've thought about swapping the 41mm carb off of my 505SX to his and vise versa to see if he even misses that big carb. The SX could use it since it likes to sing up there.
 

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Discussion Starter · #4 ·
Oh boy! Anxious to hear a ride report. I've got a ton of hours on my stock RFS head and a scarred 525 cylinder that's begging for some work and an overbore.

Dad's factory 540 kitted machine with a 806 cam and stock head feels a little flat on the very top. Even being fed with a 43.5mm carb. My gut tells me the intake valve size and cam are probably holding it back. It runs and pulls so well in the sand everywhere else we don't feel it's worth it to mess with it and make it worse somewhere else. Maybe when it's ready for a rebuild someday.... He's kind of a lugger so bottom end to upper mid range is where he likes to ride it. When I ride it in the dunes I don't notice any drawbacks either. Only when I get on a harder surface like a track do I notice it signing off on the top a bit in the overrev. I've thought about swapping the 41mm carb off of my 505SX to his and vise versa to see if he even misses that big carb. The SX could use it since it likes to sing up there.
I think you are correct. +1 head and a different grind on your cam would do well with that big carb. But first, I would definitely try switching out those Carbs between the bikes and see if your Dad likes that 41 better for the low/mid pull in the dunes.
 

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Discussion Starter · #7 · (Edited)
Is the a new KTM 540 kit? If so, that's a find. They were discontinued years ago. I used to go to CT when I lived in CA. Allen is an interesting guy.
Yea, it’s a OEM KTM 540 kit. Been holding onto this one for a very long time waiting for this re-build. Allen was kind enough to open his shop on Saturday morning so that I could drop everything off since I drove in from AZ. We talked for a while. After, dropping off with him, I took my Raptor PEP shocks to Wayne for service. Both Allen and Wayne are very interesting guys to chat with lol. I’m thankful that both are still doing what they love and helping all of us out. I was bummed that John retired from Racers Edge and Allen told me that Travis at Thumper was gone also. All three of those guys were at the top of my list to build my motor and now it seems it’s just Allen left. So that’s where she went, especially since he is doing head work on my build. I’m not sure who else, in the SW/West coast area is left that has a solid reputation for building built RFS motors. If there are other good quality RFS shops/builders out there (which I’m sure there are) it might be nice to have a thread here on the site with those shops that are still pumping out quality RFS builds.
 

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Couple years ago the local KTM dealer here mentioned they had one of those 540 kits on the shelf. I dug out my credit card REAL fast. when they brought the box out it had been opened. Looked inside and found a 450 piston and cylinder. I was pretty bummed. Likely ended up in one of the owner's hill climb bike projects.

Travis posted over on KTMtalk giving an explanation for his departure from Thumper. Dr told him he needed to give it up due to health conditions. One of his workers bought the business from him and re-named it. From the home page of Thumper Racing:

WE ARE NO LONGER TAKING ORDERS HERE


It is with a heavy heart we have made the decision to close Thumper Racing for medical reasons. Thumper's last day open is February 19, 2021. Our longtime lead mechanic and machinist, Kevin Fox, is opening his own company, Built Motors. His planned opening date is March 8, 2021. Built Motors will support Thumper Racing big bore kits with pistons, gaskets and cylinder work for refreshes. We are confident you can trust Kevin with all of your engine building and machining needs and that he will provide the quality of service you have come to expect and trust from Thumper Racing.
For any PENDING orders or service questions you can still contact us at [email protected]

It has been our honor and privilege to serve 1000's of customer from all over the world for 30+ years.
We have made countless memories and friends and we will miss you all.

Built Motors
1176 Angela Court
Suite 103
Minden, NV 89423
(775) 434-9680
[email protected]
www.builtmotors.com
 

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Discussion Starter · #9 ·
Racers Edge in Tucson was my very first choice. I thought I would have enough time before the next season started to drop off the bike and have them build the motor. I was mistaken. I called and they pretty much said it’s not going to happen anytime in the near future and to not bring the bike in as they had no room for it. First time I’ve ever been told that by any shop. They said I could bring the motor in but that it would be months before they got to it. I was super bummed and still am to an extent. John (the original owner) really went above and beyond to re-build my Raptor. My Raptor is a beast.
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Discussion Starter · #13 · (Edited)
Yes, Ive been meaning to post something up. But with the Holiday season and flu/cold and Covid putting a hurting on family and friends since early December, I haven’t really got a lot of good ride time on it. The re-build took about a month longer than promised. I have only taken her out 3 times since getting her back all together ready to ride. Two times for babying it during break in and the last trip for gettin on her pretty good. All at the Dunes. She is definitely faster but honestly I was expecting more. It does not seem to be a seat of the pants night and day difference from before which I really can’t wrap my head around right now. What I will say is that the engine is so smooth. No misses anywhere and it pulls hard and the power just keeps building very strong. Very much like the stock powerband. Overall, I am happy but I would like to get it on the Dyno to see where it stands. I was honestly expecting something violent like when I built my Raptor. But she runs good and strong it may just be deceptively faster.

Specs on the build were, Factory 540 Kit, Hot rods rod ( not really happy about that), CT +1 Valves and P&P head, Web Cam (got to double check grind) bored carb (can’t remember what bore it is) with CT jetting specs. Running 3 to 2 110 race fuel to 91 premium. Will update with all correct build specs when I look it over again.
 

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Discussion Starter · #14 ·
Tire Cloud Vehicle Sky Wheel

Took her out the last 2 weekends to the dunes. Glamis two weeks ago and Buttercup this weekend. Boy, how I was so wrong. She is fast, very fast. I got a chance to run her against Big 3 Raptors, LTZ’s and a YFZ. She mopped them all up and left them in the dust. She also ran very nicely against my extremely built Raptor. She was a sleeper and I didn’t realize how fast she actually was because it is so perfectly tuned and the power band is super smooth and usable. I feel like I didn’t give CT the real props they deserve in my last post. Allen built a hell of a fast and reliable motor for me and I couldn’t be happier with it. I just needed more seat time on her and some other fast bikes to compare her with. I still plan on getting her on the dyno and see what the build produced in real numbers but right now, I couldn’t be happier with his National 540 motor he built for me. Major Props to CT!
 

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Glad to hear it's running well for you! I've read a few articles about motor work, and sometimes a cam or engine package that produces lackluster bottom end and then hits hard in the middle/top makes the rider feel like it's better than a package that's strong bottom to top. Sometimes the butt dyno is a liar compared to the stopwatch.
 

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Discussion Starter · #17 ·
Sweet build. Glade to hear there are some reputable builders left. What compression did you end up with? I forget what the compression is on the factory 540 kit
I believe it’s 11/1. I’m going to Dyno it this Summer before next dune season and see what the numbers show. I’m guessing close to 60 rwh. I’m also planning on taking her to Wayne at PWP and having him build custom shocks all the way around. So definitely excited to see how those come out.
 

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Running 3 to 2 110 race fuel to 91 premium
Were you running "3 to 2 110 race fuel to 91 premium" with your stock motor or just pump gas? I'm asking because since E15 ethanol is going into the pump gas now and KTM says not to run anything with more than E10 in the bike I was considering running some Aviation gas (100 octane ethanol free). VP Racing sells there "T4 100 octane" fuel (actually 97 octane) that is ethanol free, unleaded. Curious if you ran anything like this in the stock motor and if so, was it worth it?
 

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Discussion Starter · #19 ·
Most of the time, I ran 4 gallons of pump 91 (with 10% Ethanol blend) to 1 gallon of 110 Sunoco race fuel. Sometimes, I ran 91 straight with no race fuel. Just depended on if I had time to stop and buy the race fuel. I would also at times run Sunoco 100 straight that they had at the pump with the 110. I don’t have any experience with AV gas but have heard nothing but great things from those who have ran it. I guess my thoughts would be to make sure the carb is properly jetted for whatever fuel you decide to run. In my part of AZ, we recently got the opportunity to start getting non ethanol fuel at the pump. I would definitely run that before I ran an ethanol blend in a stock ATV motor. Which really, even if your RFS is stock, it’s still a performance motor and I would run better fuel in it over say my daughters 250ex.

Also, to answer your question, the bike always ran a little snappier and cooler with the addition of race fuel.
 
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