Peak Seeker
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Alright, so I drilled both rivets out of the 8CR weights, and it improved things but still doesn't impress me much.
Looking at the 8CR weights, they're machined very toe heavy compared to the factory 8DF weights. And they apply a ton of force up early on, based on the weight charts in the info pages on here.
It will now pull ~8900 rpm, then fade down a bit to 8200 and hang out there. 3/4 throttle to full throttle creates no change in how it accelerates. It'll creep up to ~120km/hr on groomed trail, though the short loop i did near home doesn't give me a ton of time to wind it out before 90 degree corners.
The primary spring B-W-B may be a touch heavy, it's engaging up around 4800rpm.
Our wind loaded areas have 2-3' of soft snow to play in, and that where you notice the lack of track speed.
I'm going to now throw the factory 8DF weights with 2x 13.9mm steel rivets back in and see how it feels.
Edit after 2nd test rip:
It reacted as I suspected, considering all I've done by putting the factory weights back in is put heavier weights in...
So basically same feel, decent bottom end, smoother transition, but levels out at 7500rpm when WOT on a pull.
I don't want to drill the factory weights out because currently I'm feeling defeated and want to just put the thing back to stock.
Not sure where to go from here, 8CR weights empty with the stock Y-G-Y spring?
In my mind if it can't pull the factory weights then it must not be making the right power? I can't imagine I'm that far off on jetting.
Looking at the 8CR weights, they're machined very toe heavy compared to the factory 8DF weights. And they apply a ton of force up early on, based on the weight charts in the info pages on here.
It will now pull ~8900 rpm, then fade down a bit to 8200 and hang out there. 3/4 throttle to full throttle creates no change in how it accelerates. It'll creep up to ~120km/hr on groomed trail, though the short loop i did near home doesn't give me a ton of time to wind it out before 90 degree corners.
The primary spring B-W-B may be a touch heavy, it's engaging up around 4800rpm.
Our wind loaded areas have 2-3' of soft snow to play in, and that where you notice the lack of track speed.
I'm going to now throw the factory 8DF weights with 2x 13.9mm steel rivets back in and see how it feels.
Edit after 2nd test rip:
It reacted as I suspected, considering all I've done by putting the factory weights back in is put heavier weights in...
So basically same feel, decent bottom end, smoother transition, but levels out at 7500rpm when WOT on a pull.
I don't want to drill the factory weights out because currently I'm feeling defeated and want to just put the thing back to stock.
Not sure where to go from here, 8CR weights empty with the stock Y-G-Y spring?
In my mind if it can't pull the factory weights then it must not be making the right power? I can't imagine I'm that far off on jetting.
Last edited:
supercharged111
Member
I don't know why it wants what it wants for clutching, all I know is it's way off of stock. And my sled pulled triple digits on the lie-o-meter without me tucking behind the windshield. It's definitely faster, but you start at zero in terms of clutching. We'll see if I can get mine back together today, this was yesterday.
Or not, apparently we can't post adult sized pics to this site.
Peak Seeker
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Yeah bit of a pain you have to use you phone app or computer to reduce photo file size first.
I'm not sure what my next step should be. The sleds are all close enough even at 25 years old that one guys set up should get me close and then just fine tune from there.
supercharged111
Member
The killer is that the shift curve isn't even close to flat once the triple pipes went on. I intend to start with some 8DN-20 weights ($$$), see if that flattens it out any, then proceed to custom helixes if that won't get it done. IIRC a single custom helix is cheaper than 3 new weights from Yamaha.
Peak Seeker
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Yeah new weights are very expensive. Even worse up north here.
Which is unfortunate because I bought these new 8CR weights on SLPs recommendations.
Some adjustable weights would be nice to have but they're $400-$500 after taxes shipping and duty.
I'll put the empty 8CR weights back in today and try a dmthe YGY spring out.
Sunny here today but -24C
Have you checked the center to center on your clutches? I know from years of experience that if the center to center is higher than spec, the rpm's will fall as the speed increases.
8CR's aren't one of my favorite weights, but this sled should pull them no problem with that 51-43.
Some of the 600 twins ran these weights with a straight 47 helix and they'd pull 8000 rpm and they were only about 105hp.
8CR's aren't one of my favorite weights, but this sled should pull them no problem with that 51-43.
Some of the 600 twins ran these weights with a straight 47 helix and they'd pull 8000 rpm and they were only about 105hp.
Peak Seeker
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I haven't, I'll take a look before I go for a test ride today or tomorrow.
It's acts a lot like it did with the old belt that was worn way down currently. Though it has a new belt and proper deflection now.
What belt are you using?
Peak Seeker
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8DN
I don't know how mechanical you are, but it takes a little detail and skill to have the center to center correct.
One rule of thumb on these is that the backside of the crankcase will be up against the rubber torque stop.
One rule of thumb on these is that the backside of the crankcase will be up against the rubber torque stop.
Peak Seeker
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That's a subjective question haha.
I've got a '91k1500 with an LS and NV4500 that I rebuilt and tuned myself, and I've done 4 complete engine builds now. But something "simple" like sled clutching has me completely stumped.
I'll do some research and look into it.
I mean no disrespect, just trying to help out.
The best way without all the fancy tools is to remove the secondary bolt and install a spark plug. It will only thread in about a turn, but the reason to do that is because you can then take a tape measure and measure from the center dimple on the primary bolt to the tip of the spark plug extending from the jack shaft. 10.57 inches
Peak Seeker
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I appreciate the help 100%
Clutch offset is 15.5mm and c2c is ~268mm which, belt sticking out of the secondary is 2mm, belt width is 35.0mm so that is spot on based on the service manual.
Plugs are a little tough to read, medium brown, a touch on the fouled side after all the monkeying around clutching.
Peak Seeker
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So with empty 8CR weights and the YGY spring things improved. Engagement is almost the same, but winds out higher, still no more than 120km/hr. But up to 9000rpm then back to 8500 for a long pull.
It'll rev out to 9500rpm if it loses traction, or in loose/deep snow.
So better but still not right.
I may replace the bushing on the outer cover of the primary, another guy had a similar issue and that was his problem.
It'll rev out to 9500rpm if it loses traction, or in loose/deep snow.
So better but still not right.
I may replace the bushing on the outer cover of the primary, another guy had a similar issue and that was his problem.
supercharged111
Member
Not cheap but sure looks like the easy way to get center to center and belt deflection bang on.
www.krausekustomdesign.com
That's something I have not looked at at all, I definitely just plopped the engine in there last year once I got it together.
Yamaha SRX/SXR One Piece Clutch Alignment Tool | My Site
Billet aluminum one piece clutch alignment tool. Sets both center to center distance between clutches aswell as the offset for perfect belt alignment and cooler belt temps every time! Proudly designed and made in the U.S.A! Models also available for polaris,skidoo, and arctic cat.
www.krausekustomdesign.com
That's something I have not looked at at all, I definitely just plopped the engine in there last year once I got it together.
Peak Seeker
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Yeah I like a nice tool like that but I'd need to buy 4 more sleds to justify that. I marked center of the secondary bolt, back it almost all the way out, then used the center hole on the primary and measured between the two. Takes maybe 5 minutes. I couldn't get a spark plug to catch a thread at all.
Not cheap but sure looks like the easy way to get center to center and belt deflection bang on.
Yamaha SRX/SXR One Piece Clutch Alignment Tool | My Site
Billet aluminum one piece clutch alignment tool. Sets both center to center distance between clutches aswell as the offset for perfect belt alignment and cooler belt temps every time! Proudly designed and made in the U.S.A! Models also available for polaris,skidoo, and arctic cat.
That's something I have not looked at at all, I definitely just plopped the engine in there last year once I got it together.
supercharged111
Member
As much of a fan of freedom units that I am, it's obvious that 10.57" is supposed to be a metric measurement. 268.5mm to be exact. How far off do you need to be to create a problem I wonder? And if you err on the side of too close does it make you gain RPM with speed? I'm sure eyeballing the measurement is better than completely ignoring it as I have been.
It's been a while but maybe that was on 96 and older sleds. I think they had a larger diameter bolt.