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Kawasaki Kawasaki Tech Forum - For Questions specific and of interest to Kawasaki riders only. Questions comparing which bike is best etc go in the "Which Bike" forum.
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  #1  
Old 16 Aug 2006
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Beefing up KLR650C forks?

Has anyone done or know how to beef up the front forks on a KLR650C? Thanks.
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  #2  
Old 16 Aug 2006
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Go to the page:

http://www.bigcee.com/klr650faq.html

There is a link about how to install DRZ forks on a KLR.


You may think about using a fork brace. It's a lot cheaper and it does a good job!

Pat
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  #3  
Old 28 Aug 2006
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Smile Better shocks

Put progressive springs and a fork brace.Use a heavier weight oil.The clymer manuel tells hoe to do it.

VinnyT
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  #4  
Old 1 Sep 2006
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Thanks but the C model has 41mm forks VS. 38mm on the A model. I've found lots of info on up grading the 38mm but none on the 41mm nor have I found any after market parts for the 41mm.
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  #5  
Old 14 Sep 2006
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beef up?

I always found the KL650C forks to be ok and better than the squashy forks of the KL650A (41mm 2004 / 2005 models).
What exactly do you want to achieve with your "beef up"?
Stiffer for high speed stability?
Better response / more comfort?
Harder / more progression?
Fork bottoms out on rough road and on brakes?
The standard fork with standard springs allows for a lot of fine tuning.
There is a cure for most illnesses without replacing components.

WP suspensions never offered a replacement spring for the KL650C as they did not see enough potential to improve the forks by replacing the standard springs.
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  #6  
Old 20 Sep 2006
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I've inserted 1" dia 2" long PVC pipe conectors into the top of each fork inadditon to the stock spacers. Seems to be doing the trick and has reduce the overly soft feel and nose dive that I was trying to get rid of. I'm not yet sure if it cost me any travel.
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  #7  
Old 5 Oct 2006
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spring preload & tuning

Increasing the preload on suspension springs is amongst the worst cure for suspension problems:
You risk to permanently deform the springs by putting them under too much pressure. (They get compressed to less of the "allowed minimal length" when the fork is close to bottom out)
Your spring itself does not get harder. The spring rate is constant no matter how miuch load you put on. The preload only reduces negative travel and increases positive travel. The fork tends to "top out" on rough roads.
Not sure how pvc and fork oil go together. Fork oil is by nature rather aggressive. If you do changes with spring preload rather get a steel or aluminium tube machined.
The amount of preload you gave to your fork to sort out the problem (50mm) is a lot and points at some other cause. Measure the uncompressed length of your fork springs and compare with the length given in the manual. Fork springs sometimes start to sag when they get old and this gets worse if you preload the springs.
The 50mm preload should not cost you any travel as the spring will still be above block length when the fork is fully compressed.

As a sensible way to sort out your fork I would recommend to proceed as follows:
Check free length of springs

replace oil with standard weight as recommended by Kawasaki (oil might be too old, too little, too light.
test
increase oil level carefully. Never more than 5mm in one step. +10mm for 1st step is ok if the fork feels very soft. A max of +25 mm should solve the problem. A slightly increased fork oil level is a very good idea on many bikes if heavily loaded as it increases the progression of the fork spring rate.
Don't increase by more than 25mm as the higher air pressures in the compressing fork at some stage will blow the oil seals.
If the fork is still too soft measure the ratio between positive and negative travel with the bike normally loaded. You should have approximately 30% of negative travel with a normal load (rider + some luggage). Heavily loaded the suspensions should have not more than 50% negative travel.
If this measurement reveals that the fork springs are too soft find a manufacturer to custom make stronger ones. A spring manufacturer will also be able to calculate an allowable amount of preload you can put onto your original springs based on the value of fork travel and original preload plus the geometrical dimensions of the spring (d, D, n, l). This is easy for a linear spring, a bit tricky for a twin rate or progressive ratio spring.
Blindly I would not recommend to put more than 5% of its free length of additional pre load onto the spring.
Do not use heavier fork oil as this will make the fork feel hard and ill responding and will cost precision on bad roads.

Maybe the best solution will be slightly preloaded fork with slightly more oil.
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  #8  
Old 5 Oct 2006
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Those are some good thoughts on it. The PVC is often used by KLR650 A model owners but I'm just experimenting now. Better springs would be the correct answer but I can't find any so far. Any ideas on where to get some custom made?
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  #9  
Old 6 Oct 2006
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spring manufactures

Try to get into contact with people who race bikes or alternatively a classic bike club in your area. They tend to have the best contacts.
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  #10  
Old 12 Oct 2006
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Springs and fork brace

As mentioned above the Progressive springs are a good upgrade from OEM. The fork brace will also help the front end out. The below website has both, as well as anything else you may need for your KLR.

www.dual-star.com

Also check out www.KLR650.net.
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  #11  
Old 12 Oct 2006
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The C model has 41mm forks and the A has 38... the springs and brace will not work in the C forks.

Quote:
Originally Posted by ct_miller13
As mentioned above the Progressive springs are a good upgrade from OEM. The fork brace will also help the front end out. The below website has both, as well as anything else you may need for your KLR.

www.dual-star.com

Also check out www.KLR650.net.
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