RX-1 High RPM Not as much speed as I would expext

[blackcherrycamaro]

Purchased 03 Rx-1 low miles on it, as far as I know no mods, Played with clutching, tried Heavy hitters and Ulmer racing stage 1 kit, Motor runs great, pulls
10500 rpm immediately, tried different secondary springs , helix from Ulmer. Changing primary arms and secondary helix really woke sled up compared to stock but seems to run a lot more rpm at a any given speed than than it should, I have checked and inspected all ramps, rollers, bushings all serviceable condition or I replace if in doubt. Some people would not have issue, maybe, but it just seems to run a lot of rpm for the speed, running on regular trails in Southern WI, always 7000 to 10,000+ rpm , the sled is averaging 13mpg running this way, stock air box, had to replace seat O-rings in a couple of the carbs. Again motor runs great, but never really seems to shift down enough,
belt seems to be traveling up and down sheaves correctly any thoughts out there????

 

[maim]

Have you tried more twist on the secondary spring?

 

[misterbrutus03]

If you are not familiar with the rx's and apex's, they all have a gear reduction. Even though you are seeing 10,500 rpm your primary is only turning 8,500 rpm. Are you holding 10,500 rpm up top?

 

[blackcherrycamaro]

Yes, I can hold 10500 rpm no problem, Again I changed clutching to make sled more aggressive for the occasional drift run along the trail, the 03 factory clutching pretty lazy however the newer curved primary arms and adjustable weights made the sled aggressive, but itseems I'm always running more rpm at a given speed than seems reasonable. Rode 300 miles in the last 2 days, sled ran great except for rpm and gas mileage. Maybe I'm trying to have my cake and eat it too
Might have to reinstall factory set-up to re-establish base line???

 

[Lonerider]

rpms

to much tip weight, relocate some to heel. I have 4-0-4 on my ulmer,

 

[blackcherrycamaro]

Current set-up, STM arms Heel 4-1, Mid 0, Tip 2 ,White sec spring 6-1 Wrap, Do I really just need more tip weight? Am I thinking about this all wrong when you suggest more heel weight?? I need to amend above statement, Mid season last year changed to aftermarket silver spring equivalent 6-1 wrap, checked it today, changed secondary back to white spring, on 3-3 setting and cleaned clutch , had some improvement. Can any Rx-1 clutched owners ( aggressive trail riding)tell me your approximate speed at say 7000 rpm going down a long straight away or railroad bed 40, 50, 60 , 70 mph ??? I realize it would be a huge variable between sleds but at a maintained RPM give me your best guess

 

[Phaze]

I'm doing 40mph at 7000RPM. I have a Bender clutch kit, but don't know the specifics. I don't even engage until 5k....... I'm getting 14mpg.

 

[blackcherrycamaro]

Update and FYI, I also am running 40mph at 7000 rpm, and 13-14mpg, Had to clean primary due to dirt, debris??, Went back to white spring 3-3, kit wants 6-1 setting, however blew belt in next 40 miles, I'm starting to think I had belt issues all along which would explain a lot, missing basics can drive you crazy, ordered new Dayco XTX belt for upcoming weekend run, Also will be adding Sled dogs Cold Air box Mod to sled,

 

[smokingcrater]

, ordered new Dayco XTX belt for upcoming weekend run,

At least from my experience, I'd stick with OEM yamaha, ESPECIALLY if you are sorting out other issues. Obviously too late, but just keep the belt variable in mind for the rest of the tweaking/tuning.

 

[blackcherrycamaro]

First of all thanks to all who have responded to my posts, I learned a lot, I didn't realize their was additional gear reduction, limiting clutch rpm, next run will be this weekend, going to clean primary, new belt, probably go to 70 deg wrap as original set-up by Ulmer, question if original gearing 24/38 , Sled Dogs speed calculator indicates sled will have top end of 101 mph, is this true?, Can I ask what speed mph an 03 Rx-1 should reach at 10500 rpm on a straight run in generally . Overall the sled runs damn strong!

 

[dmaxx]

Drop down one tooth on top gear and you will be happier.

 

[blackcherrycamaro]

Update, first of all, I agree a gear change is one mod I want to do in the future, one change at a time though, cleaning the primary and setting the secondary back to 70 deg, I found something interesting, when I measured the secondary sheave distance at the top it was only 3.15, not the 3.8 to 4.1 Yamaha recommends , Closer inspection found that sometime in the past the sheave adjustment washers had been replaced with 1/4 lock washers .085 thick, maybe someone was trying to run a really worn belt?? I hope by setting it up correctly I get a little more top end, didn't look like belt traveled down as far as it should have!

FYI, While going through sled I found that all (3) the rear skid wheels had shelled bearings, put on all new and added 4th wheel kit


73 Rupp American
77 Rupp liquid cooled
570 Exciter II
94 Vmax 600
97 Vmax 600
2001 Vmax 700
2003 Rx-1

1967 SS/RS 427 Camaro!!!

 

[blackcherrycamaro]

Update, after getting some issues fixed, the sled is running scary strong!!! Still no top end though

1) Didn't understand these four strokes had the additional gear reduction
2) Skid issue's resolved, replaced all bad wheels and bearings
3)New belt, Primary and Secondary Set-up properly and cleaned
4) Added Sled Dogs air box mod, no issues in initial testing
Note new Dayco belt XTX is stickier, advertised as 4.1 Width, measured standard 3.75, brought rpm down from 10,500 to 10,200 but as I wound out it was slowly increasing.

Marked sheave, belt never travels closer than 7/16 strong from top edge, that's why it stuck in 3rd gear, suggestions, throw weight in heel???
It's been suggested that I'm geared too high and am affecting shifting due to load, ordered 23T top gear today, what else??

03 RX-1
13mm Sway Bar
Ski shims
Ulmer Clutch Kit with Helix
Cold Air Box Mod

What a great resource and website!!!
Blackcherrycamaro