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Post by mattb on Aug 12, 2007 3:37:14 GMT -5
Just wondering whether my bike's lowest cruising rpm is normal. My bike is happy at 3000rpm, but go below that and it surges and so forth, not violently at all, but enough to be uncomfortable. Do people generally find this with the SR, or does it sound like I need to service my carbie? I'd quite like to be able to cruise around at about 2500 - I like the low chugging. Can others chug not surge?  Cheers, Matt |
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Post by chew652 on Aug 12, 2007 8:02:16 GMT -5
3000 is about min comfortable RPM for me. I bought a compilation of contemporary road test and in at least one of them they mention that 3K is about the min that the bike will remain happy IIRC.
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Post by andy on Aug 12, 2007 10:28:20 GMT -5
hi matt,my theory is that top gear is quite 'tall',my sr will just about cruise at 2500,anything lower and the snatching comes into play,this isnt doing the chain,sprocckets or engine any favours,i'm also running a 17 tooth front sprocket which equates to approx 15m.p.h per 1000 revs so 2500 is 37 m.p.h quite frankly at this mundane pace [not to mention poor pick-up] i would be dropping her down into 4th.bugger the sound,dont let your engine labour.
regards,
andy
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Post by StewRoss on Aug 13, 2007 3:22:20 GMT -5
I always run with the 'not below 3,000' theory. From years of riding these things they never really seem happy below that mark. SR |
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Post by wotavidone on Aug 13, 2007 16:51:58 GMT -5
Not below 3000 on my SR.
So called "same engine" in my XT is happy at 2500.
All my mates, who have never owned one, swear blind the engines are identical.
I just nod my head and agree with 'em............
Mick
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Post by colinjay on Aug 13, 2007 17:16:54 GMT -5
Same here, my "STD" SR is running 17T on the countershaft and dosen't like going below 3000rpm in top gear, but hey, thats what the gearbox is for!
Mick, there are a few of differences (mostly minor) between the SR and XT/TT engines if you delve into them. The one that should makes the most difference in this case is the XT/TT engine has a lighter crankshaft and magneto flywheel, which should make is "snatchier" at low reves in high gears. The XT's STD final gearing is lower than the SR and that could be making the difference.
If you want a bike that can be truely be "lugged" at low revs buy an 1940-50's British 500 single. My '49 G80 Matchless 500 will idle along in top gear at about 15mph (the Smith speedo isn't very good) if you retard the ignition right back (it has a manual advance control for the magneto) and accelerate (if you could call it acceleration) away without any chain snatch.
CJ
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Post by wotavidone on Aug 13, 2007 17:55:30 GMT -5
Yeah, I'm aware of the differences, its just my arm chair expert mates who aren't.
My bikes are running pretty similar gearing.
I agree the lighter crank and flywheel should make it snatchier, but in practice, my old XT is a real stump puller.
I attribute it to the smaller carb and intake valve, combine with nearly 30 kg lighter. Are the cams different, do you know?
Mick
PS. I road a close to stock Suzuki DRZ - 400 S on the weekend. What an eye-opener.
It pulled from down low like my XT500, but just when I would be going for the next cog, this thing was just starting to hit its straps.
I could see how people could get themselves into serious strife on one.
One thing real freaky was that when you hit 100 klicks, the thing weaves all over the road. Sort of semi controlled, continuous tank slapper. But amplitude of the swings not lock to lock.
Fair dinkum, went like a rocket, but if I rode it to Clare to see you, I'd be shagged when I got there, just from steering it all the way.
Dealer said, yeah, they all do that.
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Post by miker on Aug 15, 2007 12:02:08 GMT -5
I concur with the 3000 min... anyway, I like the sound better around 4000, with the glasspack it has that great V2 buzzbomb drone.
miker
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Post by milkman on Aug 16, 2007 8:30:39 GMT -5
Mick, is that the suzuki motard or the trailie?
I've seen a couple of the motards zipping around Sydney, and they look like a great urban assualt vehicle.
BUT if they get scary at 100km, they're no good for me taking a trip home.
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Post by wotavidone on Aug 16, 2007 17:34:21 GMT -5
The trailie. Dealers own bike. They have a little throttle stop/restrictor thingy that is the first thing to be removed, followed by the bit at the back of the muffler that makes them super quiet. Without it they are loudish and startlingly quick, if you are used to our old beasties.
I believe a fairly simple damper can be fitted to sort out the twitchy bit.
I would think the motard would be a superb little all-rounder.
My personal favourite, which unfortunately I haven't scored a test ride of yet, is the DR650 dual sport.
Why, because they are as close as you can get get to a modern version of the XT500 yam.
Local dealer selling them to old farts like me by the truckload.
The guys do the following mods:
Cut and shut front pegs to drop them a bit over an inch. After market exhaust can. Raise bars one step by putting in an extra set of clamps. Bit heavier fork springs. B&B bashplate.
End result - big stump pulling thumper that can go anywhere and cruise all day at 70 mph, will pull 100mph, with 3000km oil changes like our old girls, not 500km changes like the water cooled high performance 400's and 450's.
Starting money $7600, which is bucket loads cheaper than the WR450 Yam, (about $12,000.) The 400 Suzi was about $8900, if memory serves.
Having said that, my SR and XT are so good, I simply cannot justify swapping.
So I'm not actually advocating a swap, merely observing that the great traditon of the super simple, ultra reliable, cheap to buy and run, air cooled Japanese thumper is alive and well.
My dear wife, bless her, says I can have all three if I want.
Of course, she's not paying for them.
Mick
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Post by Bize on Aug 17, 2007 4:54:56 GMT -5
They have a little throttle stop/restrictor thingy that is the first thing to be removed, followed by the bit at the back of the muffler that makes them super quiet. Yeah, the throttle stop screw is on the carb and has to be shortened. The restriction in the muffler is a sleeve that fits over the spark arrestor and not only makes it quiet, but restricts exhaust flow to only a few tiny little holes (so probably the equivenlant of having an exhaust tip as wide as a 5 cent piece. There's also a snorkel on the airbox which needs to be removed and the inlet manifold is restricted to just a tiny slit for air/fuel to flow through until you cut that restriction out of it. They are a total dog until they're derestricted and the CRF450X is just as bad with its restrictions. |
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