gpxsrx
Expert
Sr viper stock primary spring Blue Silver Blue has been updated same pre load and rate just 2mm thicker.
Also different part number, I just ordered one going to check it against my original one.
Also different part number, I just ordered one going to check it against my original one.
Last edited:
stingray719
TY 4 Stroke God
Why bother, put in a Barn Of Parts soft start spring and engage at 2600 rpm
gpxsrx
Expert
I just might do that have some clutching to do after all the mods I have done. Just no snow what so ever here in central Canada.
It sucks big time never have seen it like this ever, that I can remember.
It sucks big time never have seen it like this ever, that I can remember.
That's really odd that they would keep the same color.
Can't see it being same rate if dia is bigger.
stingray719
TY 4 Stroke God
Easy way to say "oops" without admitting it....................
gpxsrx
Expert
Read this in a factory Yamaha spec book this week. So I ordered one.
What are the spec's for the Barn of parts soft primary spring?
What are the spec's for the Barn of parts soft primary spring?
titanrcr
TY 4 Stroke Junkie
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2015 Viper LTX SE
2011 Apex
Was this in print as an updated part? Highly unlikely that Yamaha would change any aspect of a clutch spring, develop a new spring sure. Most likely what you saw was a misprint. I don't think anyone here has put the BOP spring on a tester to get the specs.
titanrcr
TY 4 Stroke Junkie
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Well I guess I'll "Walk That One Back"....Just checked it out and it seems they have made a change to the BL/SL/BL primary spring. Updated the part number as well. I might try one in my Apex, it also uses BL/SL/BL. I would think that the number of turns and free length would have changed to maintain the same forces as the original. Original Part #90501-551L9-00 Now #90501-570A0-00 Go Figure ?
Notenoughtoys
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Just installed the b.o.p soft start springs in both vipers. Engages around 2700 rpm....smooth as butter!!!
gpxsrx
Expert
Could not remember if the part number was changed or not was going to clarify at work tomorrow.
stingray719
TY 4 Stroke God
Not that I know of anyways. BUT, I ran two Vipers with GWG with shims and then changed out to BOP spring with same shims in one Viper and ran them again and could not tell any performance difference....not scientific but good enough for me.
Hillbilly2015
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I broke 4 factory springs last season in my 15 stx. Dealer said that yamaha was updating the spring. I just bought ulmer clutch kit. No more screwing around.
titanrcr
TY 4 Stroke Junkie
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2015 Viper LTX SE
2011 Apex
I think the BOP spring is advertised as a direct replacement for BL/SL/BL in a stock viper. That being said the BOP spring should have a total force very close to the BL/SL/BL (stock viper) which would be 101kg at full shift. I say that because I'm sure they want to maintain the correct shift speed. The GR/WT/GR spring is 136kg at full shift, very different, but at the end of the day the only thing that really matters is the riders preference. At this point I think that most riders would prefer a soft engagement and lower cruising RPM provided by the BOP spring over other setups. For a guy who wants go line up on the lake with his buddys it's probably not the best choice. All depends where and how you ride......
stingray719
TY 4 Stroke God
BOP soft start spring was designed as a spring replacement for the Apex, so much stronger than BSB it is not even a comparison, i suggest you buy one and measure it. Increasing spring pressure even in a totally stock Viper makes better shifts, see the full details in the Clutching on the Cheap FAQ at top of this forum.
