Rebuilt RX1 update after a really short season of riding.

[NLP_SLED_GUY]

Hello all, I posted originally about buying and fixing up a 03 RX1. Well I spite of a miserable snow season I did manage a few rides On it. A few I was riding it and three rides with friends riding it.
First I’ll say I’ve decided to keep it And put a little more work into it.

The feedback from all of the others was very positive. I got the sled steering decently tight and the suspension fairly well balanced. No darting issues. It has Simmons flexi skis with new 4 and 6 inch carbides. Sled has been extended to a 136. I put a low mile Cobra track on it. This sled has a lot of upgrades. I’ll mention where relevant. With the 13 mm sway bar the sled actually handled better than I expected.

First ride of the season was a couple hundred miles around Newberry, Mi. It got 11.5 mpg and burned about 1/3 of a quart of oil. Not what I’d hoped but it was otherwise trouble free. This was with new K&N filters, 165 main jets and silver springs. Sled came this way I just replaced the filters as the original ones were in bad shape. With this carb setup the sled runs very poorly below about 5000 rpm. I didn’t like it and neither did any of the other riders. So after the trip ordered some gre3n CV springs and restored the stock intake setup, witch did come with the sled. After syncing the carbs it was much smoother. My only remaining carb issue is properly adjusting the pilot screws. I did manage to get them adjusted a bit and that really helps smoothen the engine at tip in And down low. But the screws are almost impossible to get at. More on that later. Dropped the needle clips one position. I am using a wideband. The sled was run this way for the remainder of the season.

But after the trip to the UP I read some here and decided to give the engine the seafoam treatment. As instructed in the tank and the crankcase. I have used seafoam before and no kidding had really good results with it in older engines, mainly freeing up sticking valves. I ran the sled for about 100 miles (tank full of fuel) and changed the oil. Man it really looks like it gets the crud out. Put maybe another 200 miles on it after that and it didn’t lose a drop of oil. But all of these changes only improved fuel economy to about 12 mpg. But that may have been with more experienced riders. it still needs minor carb work. But more on that at the end.

Finally got to line this RX1 with my 2019 Doo GT-L 600R. All of the two up gear stripped from it. From a dig it’s not really even close. The 600R leaps out to several lengths. And holds them till maybe 70 and the RX1 starts to make it up. 80-85 mph the RX1 has finally caught up and is passing. Once passed the point is proven so not much more speed than that. Se we did that a couple times with the same results. Then from a 25 mph roll. The first time it was side by side with the RX1 about half a sled up and creeping. Then at around 80-85 the RX1 exerts its power and creeps away. Then a second time from 25 mph. This time I think my son got a better reaction and the RX1 jumped up and took off on me by several sleds and stated going away. Under 75-80 the 600R is solid. It just runs out of nuts up there. I’ve had it to 100 mph on the Speedo. But after 80 you are gonna need some room.

A few days later I took both sleds out by myself and rode them back to back. The new Doo is a better sled in most ways. That’s to be expected. But the difference isn’t worlds apart. I like both sleds. The doos smoother ride has me favoring it because I’m old and broken down. Anyway, I managed to run them both up to my nerve that day. The Doo is just like I mentioned. Leaps to 75-80ish then you start to wait to see the speedo climb. At 80 the RX1 was pulling like it was still at 60. A second later it was at 95 and Speedo is jumping 4-5 mph an Speedo update! It never let up its pull till I let off just over 100 mph on the speedo. The sled does have Full primary and secondary clutch treatments by Chris Schmidt. on initial hit the RPM jumps to about 9800-9900, but as the track spin reduces it goes up to 10,500. The noise is chub worthy. I like it. One big difference is the incredible amount of track spin the RX1 has. I’m sure that this was a big factor in running the 600R. i know you can make the Yamaha transfer better but it’s not a priority. WOT isn’t how it’s going to be ridden normally.

After deciding my season was done I recounted the teeth on gears. The upper had been reduced by two teeth. 22 vice 24. This may explain some of the track spin and the reduced fuel economy. I found a NOS stock gear I’ll swap in before next year. Another goal is to get the carbs tuned correctly for the K&Ns as well as to find a way to properly adjust those whacky pilot screws. I’ve tried several suggestions I saw on the web but none of them worked well enough to adjust all 4 cylinders. I have an idea or two.

Overall I’m happy with it. it’s a good sled that should last a while. I’m gonna work on refining a few rough edges and work on it’s appearance a bit.

I apologize for the novel but you didn’t have anything better to do anyway!

Thanks!

 

[74Nitro]

You should be able to dial it in nicely with the wideband.
What are the readings?

 

[STAIN]

Also try a little Yamaha "ring free" for the oil burning problem. That stuff is really good.

 

[NLP_SLED_GUY]

I used some Seaform and it seemed to work just fine. A couple hundred miles since the treatment and no oil loss.

 

[NLP_SLED_GUY]

You should be able to dial it in nicely with the wideband.
What are the readings?

That is kind of a long answer.

After playing with most of these different spring and air filter/airbox configurations I started to read up more about how the CV carbs work. My suspicions were that the CV springs just aren't right. Before I started chasing tuning I really wanted to know where Yamaha had intended the engine be run at. Since the only things that are longer stock are the CV springs and one needle cIip position. I started looking for some. The big symptom that lead me to think this is the mixture. With everything being bone stock, including the pilot screws at 2 turns (as per the manual and one clip leaner on the needles) the mixture at idle is 13.0:1 with green springs and stock air box, 12.0 with red and silver with K&Ns (165 main jets). It's pretty much that way all of the to WOT. But I admit I haven't actually recorded or datalogged up that high. Just short hits to get an idea. Obviously this isn't very optimal. And it's like this with just about any aftermarket spring too rich. I just know that Yamaha never intended this. There's no reason. Is this maybe why so many have issues with sticking rings and carbon?

So I first attempted to get 4 new, stock CV springs via parts dealers. I managed to get two. I was told "good luck" finding any more as the are "no longer available". I managed to find one more on ebay. So I'm at three. All three are still in Yamaha packaging and labeling. But the fourth has been elusive. So yesterday while I was in Midland, MI I stopped by Mickey's Sleds to see if they happen to have one. Turns out they have a full RX1 rack intact. So I bought all four springs. I may go back later to buy the entire rack. They matched perfectly to the length and turns to the new factory springs.

This morning I put them in before to get a test ride in before yesterday's snow melted. The idle mixture was still where I had it the last time I was playing with pilot jets. About 13.0:1. This is expected as the CV slides should be fully closed and only the pilot idle circuit supplying fuel. Still too rich, but I got tired of taking the carbs off to continually adjust the screws. Like I mentioned I'll get to that. From prior sessions I have determined that about 1.5 turns out will put the mixture aright around 14.0-14.5. That's where I intend to go with the screws the next time I feel like taking the carbs off. But this consistency indicates to me that the CV slides are completely closing with at least the green and stock springs. I have suspected that the silver springs may actually be slightly open or bouncing a touch at idle. But I have no proof of this.

What did change considerably was the mixture tip in and up. Prior silver springs were always at 12.0:1 and green about 12.8-13.0:1. With the stock springs it is now 14.5-14.7 most of the throttle range until fully into the main jets. The full shift mixture was around 12.0:1. But I have less confidence in this reading simply due to the duration and my ability to see the reading. But It sounds reasonable from the factory. If this was a car with fuel injection I'd go a bit closer to 13.0:1. Next season when i get a chance to get a more stable reading I'll decide if any WOT mixture changes are in order, maybe going back to stock needle setting as I'm already one notch up on the e-clips. All of the "Burble" or missing thru tip-in and engagement are completely gone. The sled is glass smooth everywhere and runs as I would expect a perfectly running 4 stroke should run. With the room I have on my property I didn't notice any loss of responsiveness. Actually, maybe better. With the aftermarket springs I noticed that if you nailed to WOT let it shift up then let off and hit it again, there was a dead response that was only a faction of a second. It didn't do that today. The stiffer springs maybe closing faster. ??? Instant flash rpm is exactly the same. I will work on getting access to the pilot screws so they can be fine adjusted. But other than that I'm considering this sled fixed. If I get bored next season and we actually get some snow maybe I'll play with tuning the on carb filters to work properly. But I doubt it. At this point I'm not worried about about a few extra ponies. Proper ridability and fuel range is more important.

My opinion in summary. The purpose of the CV slides is attempt to generate constant velocity thru the carbs by being a relative restriction to increase throttle response and torque. The fuel quantity being mostly controlled by the CV slides is critical to the mixture. Opening the slides earlier or easier may actually hurt maintaining constant velocity as well as deliver more fuel enrichment than desired. I realize that the changing of springs is to offset the loss vacuum signal at the front of the carb due to the loss of restriction from front side modifications. It's more complicated than simply changing the springs. The engines' airflow, spring opening rate and jetting profile are all dependant on one another. That means the springs and all of the jetting need to be RIGHT. This includes pilot jets and the needles and needle seats. True top-down re-calibration would be required...IMHO. Honestly, I don't have the time, patience nor desire to accomplish this for so little return. This is exactly why I was happy to dump carbs fore EFI back in the day. The same goes for vinyl and CDs. Your opinion may vary.

The green springs were the closest and usable. Is the loss in fuel economy/range worth little to no response improvement? 12.0 to 14.5 is 21% more fuel and 13.0-14.5:1 is almost 12% more fuel usage in the most important range of operation. That potentially turns at 11-12 MPG sled into a 14.5 MPG sled. Could you use an extra 24-25 miles a tank while riding around the UP? When I bought the sled everything I read had me expecting at least 14 MPG. I expect that is more realistic now. I think getting that gearing back to stock might help a bit more.

I have read many have claimed a gain in fuel economy with these "ECP" kits. Based just on my particular sled years later I'm skeptical. But who knows? I always reserve the right to be wrong.

I've ordered a few parts for backup and appearance. While I think I have the rear suspension working very well, I am considering a rear end swap. Anyone ever put at 136 inch track on a 137 inch R-Motion rear? Seems like it should work!

Thank you all for the support.