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Old 06-03-2007, 11:30 AM   #1
klm4755 OP
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KLR650 Front Sprocket swap step-by-step Walk thru

Enclosed is a step by step walk thru to swap out the KLR650 front (drive) sprocket (15 tooth) with a 16 tooth PBI “after-market” brand. Since 99% of the KLR travels will be on pavement during my daily commute, I am seeking a less vibration environment. One way to obtain this effect is to lower the RPM’s while in 5th gear. The larger sprocket will reduce RPM’s by 7% for the equivalent speed. Do not loosen rear wheel or mess with the chain...yet
Sprocket can be seen here:

http://happy-trail.com/ProductInfo.aspx?productid=MCY%2050-440XX


sprocket as delivered from happytrails.com


annotations on packaging


exploded view of configuration. Note represents a 2007 bike.


remove sprocket cover


The bolt to remove....27mm socket size.


pry back the retainer clip. Easy to bend with prying screw driver


like so



since a 27mm socket is very difficult/expensive a 1 and 1/16 size socket will fit.


Ok...the tricky part.
1. Place the bike on the side stand
2. Approach bike from right side and lean over placing your belly on the seat.
3. Right foot on rear brake...push
4. Right hand on front brake ...squeeze
5. Left foot on ground
6. Place socket on sprocket nut. Wrench handle pointing aft (toward rear). Left hand on wrench handle.
7. Lift left hand with all might to loosen nut. I used a 2 foot ˝ torque wrench as shown above


spin nut off of threaded drive shaft


like so...now jack up bike, remove rear axle and loosen chain


drive stud with sprocket on splines


backoff view


wiggle sprocket off splines. Out view side


inner view side


proper stack-up sequence


spline with sprocket off..inspect..no wear here. My bike has 2,000 miles logged


height comparison


top view OEM 15 tooth over 16 tooth new


new sprocket installed on spline


add nut retainer and thread nut


torque nut to 72 ft-lbs note units!


bend the retainer over the nut land area, use channel lock plyers


like so


replace sprocket cover, rear axle nut to 69 ft-lbs, and adjust the chain to spec.


cleaned up OEM sprocket


little to no wear after 2,000 miles



Observations and Review:
1. Easy to swapout
2. Loosening the sprocket nut was the most difficult part
3. Little to no sprocket wear after 2,000 miles
4. Love the way the bike “feels” now
5. Feels like the 6th gear the bike has been missing.
6. Don’t miss the low end torque ...yet. Worth the trade for me.
Keithm
-----------EDIT Below------
I have reviewed the install have included the option to shim and included a progressive torque nut from Arrowheadmotorsports.


progressive nut + 30mm socket for install


closeup of nut.


Note the crimped threads


sprocket shims


OEM sprocket “Bike side” shown


shim ID


shim OD


would fit here, if needed


sprocket gage at shaft location = .500 inch


PBI aftermarket sprocket gage at shaft location = .501 inch, matches


Will flip PBI sprocket and compare with OEM


try this, outside view


inside view


teeth align in this orientation. NO shims needed!


reinstalled with PBI markings inside


torque to 72 ft-lbs


I’ll still use the supplemental nut locking device, just for extra safety


fold over a tab


OEM fasteners replaced

The PBI sprocket is an exact match without shims. Face markings on the inside face.

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Old 06-03-2007, 11:32 AM   #2
Max Kool
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Very well documented!!

Max Kool screwed with this post 06-03-2007 at 11:38 AM
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Old 06-03-2007, 11:37 AM   #3
shoco
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Excellent write up. Thanks for taking the time to post this!
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Old 06-03-2007, 02:28 PM   #4
dgunther
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Nice write-up.

I realize the need to make do with what is on-hand, but it is best not to use a torque wrench for breaking loose the sprocket nut. You might damage it or cause it to fall out of calibration, increasing the chance that you could over-torque something important in the future.

I use a cheap extendable 1/2" breaker bar I picked up at Harbor Freight or Northern Tool - you can try to mess up a whole bunch of those for less than the price of even the cheapest torque wrench!
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Old 06-04-2007, 05:48 PM   #5
klr650tr
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how about 17teeth?
too much? anyone has it?
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Old 06-04-2007, 06:03 PM   #6
Kbetts
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I didn't put the locking plate back on with the prevailing torq nut....

I thought the whole idea was not to need a locking plate for field swaping the CS.....

Do I need to take the PT nut back off and stick the locking plate behind it and bend it over?

Keith
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Old 06-04-2007, 06:15 PM   #7
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The locking plate is not needed with the prevailing nut. That's the joy, just use a crescent wrench or something similar and you don't have to go through so many steps to change sprockets. I can change sprockets (13 tooth) on two bikes ( mine & my wife's) in about 30 minutes when we are going offroading. The prevailing nut is awesome.
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Old 06-04-2007, 06:34 PM   #8
klm4755 OP
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The lock washer was just added for additional security. You know, I dress with a belt and suspenders.
Keithm
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Old 06-13-2007, 06:46 PM   #9
East Coast
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Appreciate the indepth explanation

Just tried to do the gear swap this evening - "prior to reading this article", and was not sucessfull due to inability to get the nut off. I'll try your method. Did you make any changes to your chain tension?

Thanks. Jt
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Old 06-13-2007, 07:48 PM   #10
klm4755 OP
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Yes, the rear axle was moved forward just a tad to compensate for the slightly larger drive sprocket. No new chain needed though. Still very happy with the extra tooth.
Keithm
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Old 06-14-2007, 07:41 PM   #11
East Coast
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Question

Why did you remove the rear axle. Did you just loosen it to move it forward?
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Old 06-20-2007, 05:49 PM   #12
klm4755 OP
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I removed the rear axle so I would not have to re-thread those chain adjusters. I have the fuji lockbolts.
Keith
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Old 06-20-2007, 06:17 PM   #13
CA Stu
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Question



Hey man, I'm pretty sure that those washers are for the early model bikes (pre-96) that used a different method of mounting the drive sprocket that was prone to chatter and wearing out the splines, not for your bike...

Do some homework and get back to me!

Thanks
CA Stu

EDIT: from the FAQ:
Mid-1996: Changed valve cover, added bracket to hold cam chain bumper; changed crank to heavier unit; improved clutch basket with more clutch plates; changed countershaft sprocket retainer from slotted plate to large nut; changed 2nd and 3rd gear ratios. Kickstarter no longer fits with new clutch basket

On '95 and earlier models, two hex head screws hold a slotted retaining plate. Remove the screws, rotate the plate, and pull it off. Note that the retaining plate can get chewed up. Sagebrush Machine Shop makes a stronger replacement part, that gives full engagement of the splines rather than half.

I believe those washers were sold as part of a remedy for this problem.


And not to come off like a know it all, but even with zero maintenance, a stock OEM sprocket is good for at least 15k miles, the chain maybe 9 or 10k miles, and it's best to replace all 3 items (both sprockets and the chain) at the same time.
Preferably before they look like this:

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CA Stu screwed with this post 06-20-2007 at 06:26 PM
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Old 06-20-2007, 10:55 PM   #14
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Free advice is worth what you pay for it, but...

Um, what is the point of bending the washer over the prevailing torque nut?

It's silly.

A bent splined washer isn't going to magically flatten itself out and allow a sprocket that is on a splined shaft to fly off.

Are you now or have you ever been inside a garage?

Thanks
CA Stu

PS here are my instructions

1) remove old sprocket
2) Install new sprocket
3) Go riding


And, FWIW, I've tried other tooth count front sprockets, and here is my conclusion;

The 15 is the best for every day riding.

If you are one of those morons that enjoys thrashing your KLR where it should never go, the 14t is really good (sweet spot in rpm and speed for tough offroad in 2nd gear), and the 16 is OK if you live in Florida and hardly ever use your clutch.
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Old 06-20-2007, 11:23 PM   #15
wheatwhacker
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Wow, what a great article...........
I did mine a year ago, went as follows.

Step 1. Loosen rear wheel and slacken chain a little.
Step 2. Take off 15 tooth sprocket.
Step 3. Install 16 tooth sprocket.
Step 4. Retighten chain, tighten rear wheel.
Step 4. Check for gas, start motor, ride.

Total time..............15 min
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