FAQ Section - Frequently Asked Questions
NOTE: The KTM50 jetting specs are for Pro Senior bikes. We do not work with air cooled 50's. The 14mm carb on the Pro Jr. is difficult to jet. Normally they require going up 1 size on the pilot jet. We DO NOT STOCK Pro. Jr. jets. Call your local KTM Dealer to get jets for your Jr. or any other genuine KTM parts.
KTM Setup Tips - 2009 -
2010
Oil = Maxima K2, Silkolene Comp2, Yamalube R (There are many good oils out there. Have have had exceptional luck with
these oils in the tank)
Fuel = 93 Octane pump gas (whoever tells you to run race gas in a 50cc is
WRONG!)
Ratio = 40:1 , that's 3.2oz per gallon
Plug = Stock spark plug is fine
Main Jet = Stock
Pilot Jet = Stock
Needle Clip = 2nd from top
Air screw = 2 1/2 - 3- 31/2 most of the time. If you have to
go more than 4 turns out to make the bike run right you will need a larger pilot
jet.
Clutch = For most riders add .0030 worth of clutch shims under each clutch spring to increase the RPM stall. Note - every .0010 equals a 100 RPM increase in clutch stall.
Set idle as low as you can for improved throttle response!
Sprockets = Stock from and a 38 rear for most riders, DID415ER chain
KTM Pro Sr. LC50 Jetting - 2001 -
2008
Oil = Maxima K2, Silkolene Comp2, Yamalube R (There are many good oils out there. Have have had exceptional luck with
these oils in the tank)
Fuel = 93 Octane pump gas (whoever tells you to run race gas in a 50cc is
WRONG!)
Ratio = 40:1 , that's 3.2oz per gallon
Plug = BR9EIX (go with a good plug, get it jetted right and your plug will last for months)
Main Jet = Stock bike 86 - 88 main jet, most of the time a 86 main. Modified 60cc and larger LC's 88 - 92
most of the time a
90 main.
Pilot Jet = 50 - 55 for both stock and mod bikes. Most of the time a 55, next the
52
Needle Clip = 2nd from top
Air screw = 2 1/2 - 4 screws out, 3- 31/2 most of the time. If you have to
go more than 4 turns out to make the bike run right you will need a larger pilot
jet.
Slide = The stock slide works great in all area's of the country. If your bike runs better with a another slide your jetting was probably not set correctly.
Set idle as low as you can for improved throttle response!
KTM 50 Gearing - 2001 - 2008
Throw that stock chain away before you do anything!
12 tooth front / 45-47 rear, a 46 90% of the time
DO NOT USE CHAIN LUBE - WD-40 ONLY!
We recommend an DID ER 415 Gold Racing chain as our 1st choice and a Renthal Racing 420 chain as 2nd.
Aluminum sprockets for the rear.
KTM LC50 Clutch Setup - 2001 - 2008
WE DO NOT RECOMMEND THE USE OF STAINLESS STEEL WASHERS IN 2001 - 2008 KTM 50's!
First off not
all clutch washers are the same size. Even
a new bag of 1000 washers comes with variable size washers in it.
It is not the size of the individual washer that matters. However, it is crucial that all overall washer stacks are the
same height!
The taller the
washer stack the higher the engine stalls (more RPMS) before the clutch engages.
The lower the washer stack the sooner the clutch engages (too early will
create a bog). There is a fine line
between getting the bike to engage at its best and overdoing it and causing
clutch drums to break.
To setup a
clutch properly you will need a set of calipers to measure the stack height.
I have seen inexpensive plastic ones in the auto parts stores for around
$5.00.
I normally
setup racing clutches to an overall height of .650 - .690 depending on the
rider’s weight and track type. If
you stay in that range you should be happy with the results.
A good place to start would be if your rider weighs 50 pounds stay around
.650, 60 pounds .670, over 65 pounds go for the .690 setup.
I am calling the overall height that of all the cupped washers and flat
washers together.
Now we get into
the options. A setup that uses a () setup vs a (()) setup.
A () setup will throw the clutches quicker a feel a little more
responsive than a setup that used (()) washer stacks.
In the warmer months a () setup seems to breakdown with heat much quicker
than a (()) setup.
Suggested
Summer setup – (top of bolt on this end)
(())(())(())() plus the flat washers.
Suggested
Winter– (top of bolt on this end) ()()()()(((((((
plus the flat washers <requires an additional cupped washer>.
It is very
important to ensure that ALL THREE WASHER STACKS are of equal height.
If 1 or 2 clutch pads hit the drum before the others you are losing
hook-up ability.
The bottom line is you will normally need to experiment to get YOUR RIDERS clutches they way they want it. Use the suggestions above as a good STARTING POINT. Clean your clutch washers often. The difference in a holeshot and no-holeshot is greatly due to the clutch in your 50cc bike. I don’t claim to know it all, but the bikes I build have pulled hundred’s of holeshots on across all levels of competition. I hope this helps your racer to do the same.
There are many variations of washer setups. These recommendations are for experienced riders who expect a holeshot. These would be stacked with the left side against the head of the bolt.
Use blue loctite on the clutch bolts and 1 drop of red on the clutch and crank shaft.
Use 8oz on Maxima MTL Extra Light 75wt oil in the crank case. I can promise you that anything else is 2nd best.
Note: These are suggestions that work well for a number of riders. DON'T BE LAZY, take the time to learn YOUR clutch. If your bike does not hit well AFTER following ALL the above steps you may need to fine tune it. You will have to do that. We do not provide clutch stack support via the telephone. If you have a question please email it to techsupport@thracing.com and we'll do what we can to get you a timely answer.
Can I make my KTM 50 faster ?
Absolutely! T H Racing can build a bike to you riders ability and riding conditions. We can produce up to a 30% increase in performance of stock. These bikes are race only and not for the budget watcher.
What can I do if I ride my motorcycle in the stock class?
T H Racing can add legal power to your stock class bike. In some cases close to a 20% increase in power. Typical results are in the 16% - 18% range, call us at 817-713-6989 for more information.
KTM 65SX Jetting 2009 - 2010
Oil = Maxima K2, Silkolene Comp2
Fuel = Straight 93 Octane pump gas
Ratio = 40:1 , that's 3.2oz per gallon
Plug = Stock
Main Jet = 195 - 210
Pilot Jet = 25 - 27.5
Needle Clip = 2nd clip from the top of the needle position
KTM 65SX Jetting 2006 - 2008
Oil = Maxima K2, Silkolene Comp2
Fuel = Straight 93 Octane pump gas
Ratio = 40:1 , that's 3.2oz per gallon
Plug = Stock NGK BR8ECM
Main Jet = 210 - 220
Pilot Jet = 32.5
Needle Clip = 2nd clip from the top of the needle position
KTM 65SX Jetting 2002 - 2005
Oil = Maxima K2, Silkolene Comp2
Fuel = Straight 93 Octane pump gas
Ratio = 40:1 , that's 3.2oz per gallon
Plug = Stock NGK BR8ECM
Main Jet = 230
Pilot Jet = 35
Needle Clip = Middle position
KTM 65SX Gearing
Throw that stock chain away before you do anything!
98-01 bikes 13 tooth front 46 rear on stock bikes
2002 - 2010 bikes 14 front 48 rear on stock bikes
2002 - 2010 bikes 14 front 47 rear on mod bikes
KTM 85SX Jetting 2003 - 2009
Oil = Maxima K2, Silkolene Comp2
Fuel = Straight 93 Octane pump gas
Ratio = 40:1 , that's 3.2oz per gallon
Plug = NGK BR9EIX
Main Jet = 115 - 118
Pilot Jet = 45
Needle Clip = Middle position
KTM 105SX Jetting 2005 - 2010
Oil = Maxima K2, Silkolene Comp2
Fuel = Straight 93 Octane pump gas
Ratio = 40:1 , that's 3.2oz per gallon
Plug = NGK BR9EIX
Main Jet = 118 - 122
Pilot Jet = 45
Needle Clip = Middle position
2002 - 2008 KX 65 Jetting
Oil = Maxima K2, Silkolene Comp2
Fuel = Straight 93 Octane pump gas
Ratio = 36:1
Plug = Stock NGK BR8ECM
Main Jet = 190 - 200
Pilot Jet = 27.5 - 30
Needle Clip = 2nd clip from the top of the needle position
2002 - 2010 KX 65 Gearing
Throw that stock chain away before you do anything!
Throw that stock chain away before you do anything!
2002 - 2008 bikes 14 front 48 rear on stock bikes
2002 - 2008 bikes 14 front 47 rear on mod bikes
Note - If your rider weighs over 80 pounds with gear on add one tooth to the rear.
Yamaha YZ85 Jetting 2002 - 2005
Oil = Maxima K2, Silkolene Comp2
Fuel = 93 Octane pump gas mixed 50/50 with VP U4 race fuel
Ratio = 40:1 , that's 3.2oz per gallon
Plug = NGK BR10EIX
Main Jet = 135 to 138
Pilot Jet = 45
Needle Clip = 2nd from top most of the time position
Yamaha YZ85 2002 - 2010 Gearing
Throw that stock chain away before you ride it!
14 tooth front 48 rear on stock bikes 47 on modified bikes.
Honda CRF150R Jetting 2007 - 2010
Main Jet = 138 - 140
Pilot Jet = 45 -48
Needle Clip = 2nd clip from the top of the needle position
What are some of the areas that I need to pay attention to?
KTM 65 owners - On ALL KTM mini's use Motul 5.1 brake fluid. 5.0 DOES NOT CUT IT!!! Replace your waterpump shaft, seal, and bearings with a T H Racing water pump solution kit, BEFORE you have a problem.
KTM 65 owners - Make sure to use nylon thread tape on your clear oil site plug on the clutch cover. These heat at a different rate than the cover and are prone to falling out. Replace the chain adjuster bolts with bolts that are at least 1 1/2 time as long to prevent breakage of the internal nut. Use green Loctite and longer bolts in your silencer end cap to prevent losing it! Put red loctite on your kick starter bolt BEFORE you lose it. To improve clutch feel and longevity of the clutch bleed the mineral oil out of the master cylinder and replace with synthetic ATF. We use Mobil 1 AFT with good success. Watch your clutch basket! Several of the 2002 on up models have come with loose drive gears on the clutch basket. Unfortunately, there is not much you can do short of replacing the clutch basket if you have a bike with the problem. It is quick and easy to check for. Remove your oil fill plug. Using a flat blade screw driver wiggle your basket forward and backward. If you have more than 3/16" free play you will need a new basket soon! Brakes............ they can be a problem. Replace your pads with bronze sintered pads. 2004-2005 bikes wear rear pads FAST!!! Get a few sets to have on hand. In 2004 the rear brake was changed and uses the same pads as the 2002 - 2005 LC50 front pads. Keep an eye on the crankcase vent hose (its the dark gray hose on the back of the engine). If it becomes blocked with mud or smashed by putting the bike on a stand it CAN cause excessive pressure and push oil past the water pump seal and into the radiator. Take a look at the bolts holding the brake line to the fork protector. You will notice one is too long and will scratch up or gouge your fork leg. Replace the bolt with a shorter bolt or add a couple of washers and reinstall the bolt.
KTM LC50 Owners - Inspect and replace the water pump shaft before you have an overheating problem. 2002 - 2008 LC50 owner should inspect their upper chain guide on the swing-arm BEFORE even starting the bike. There have been many cases of thrown chains . We have found that a quick, simple, an effective fix is to cut a 1" piece off the end of a zip tie. Loosen the bolt that holds the upper chain guide in place and insert the under the edge of the guide near the bolt. Most of the time the zip tie should be placed to the right of the bolt. When you tighten the bolt it will shift the guide into alignment. Experiment as to what works best to align your chain guide. Roll the back wheel forward to make certain the chain is tracking well before riding.
KX65 Owners - I recommend a complete tear down and loctite and grease everything on ALL bikes before riding them. If you are strapped for time, there are 2 bolts that need blue loctite BEFORE you ride your bike. The kick starter bolts and the lower chain roller! Most Kawasaki's come with very light grease and no oil on the air filter.
YZ85 Owners - Loctite the bolts in the silencer canister before you loose them. Use a mix of VP U2 or other oxygenated fuel and pump gas to get rid of the flat spot on the off idle bottom-end. Keep a complete clutch on hand because you will need it at some point. Make sure you keep free play in the clutch cable.
All Bikes - We recommend Twin Air air filter oil. It has proven time and time again to make the most power in out dyno testing. The worst filter oil you can use from a performance standpoint is the spray on oils. After you think your air filter is clean, try a little Simple Green and warm water on it and watch the dirty water wring out of your filter. We use and recommend Mobil 1 0W-30 oil in the transmissions of all shifting bikes. Clutch life and shifting smoothness are at there best with Mobil 1.
Check back - The FAQ section will be updated on a regular basis.