Could use some Help please

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Could use some Help please

Post  SMXR on Tue Sep 06, 2016 8:51 pm

I have two xr650r's one in dirt clothes and one supermoto. My Xr that has dirt tires is a beast has WAY more power than my supermoto and i cannot figure out why. When i bought the SM i knew it didn't feel right the power would surge on acceleration I figured it to be jetting problem. Jetting from previous owner was main 160 pilot 72 (My altitude is mostly ridden around 6,000 to 8,000). I bought it from dealership so I have no background info on work done. Based on a uncorked stock bike and my altitude my jetting should be 160/65. On my dirt Xr uncorked with full fmf exhaust, air box restrictors removed, no holes drilled in air box, my jetting is 165/65 3rd clip and hauls scary ass. I tried this same jetting on my XR SM and its a slow dog feels like my 1986 xt600 (maybe not quite) bogged under half to full throttle would not power wheelie first gear. Since then i have changed jetting one by one with lots of testing. I am now running 170/68s needle 3rd clip and it is running much better but no where close to my other XR.

Considering the jetting I use for my dirt XR didnt work I am thinking maybe the XRSM has engine work explaing why its running better with larger jetting or it could just be the K&N pod filter.

I really want to get my SM running right and i know there is plenty of knowledge on here so thank you. If i need to re-post this under different section please let me know.

2003 XR Super slow moto:
Engine upgrades - Un-known
Stock air box removed and round K&N filter installed
Arrow headers with Yoshi RS3 slip on
Jetting 170 main pilot 68s needle 3rd clip

2002 XR dirt (runs great)
Engine-Stock
airbox restrictors removed (no holes drilled in cover)
FMF Power bomb headers with FMF titanium 4 exhaust.
jetting 165/65 needle 3rd clip
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Re: Could use some Help please

Post  Mauser on Tue Sep 06, 2016 9:11 pm

Why not swap the carb from your other bike ?...not massive job and that would at least tell you what's @ fault ?, sorry not really into performance faults like yours so cannot help much Smile

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Re: Could use some Help please

Post  SMXR on Tue Sep 06, 2016 10:33 pm

I do not think that changing carb is going to change anything but i will try. I already duplicated the jetting and the SM ran better than when i got it with a 160 main. Since then i have changed each jet one by one testing each change in between. The larger the main I put in it the better it runs I am up to 170 which is rich for my altitude depending on mod's. I just ordered a 172, 175, 178 to see if it gets where it needs to be. I will be adjusting/checking valves today and going to rent a compresion checker from autozone to check compression.
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Re: Could use some Help please

Post  Mauser on Tue Sep 06, 2016 11:08 pm

Maybe the pod air filter is letting too much air in ?, when I got my bike it ran terrible compared to now as someone had removed the foam filter and just left the gauze screen in the air box. I think way too much air was making the mixture miles off... does that make sense ?

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Re: Could use some Help please

Post  SMXR on Wed Sep 07, 2016 1:04 am

Mauser wrote:Maybe the pod air filter is letting too much air in ?, when I got my bike it ran terrible compared to now as someone had removed the foam filter and just left the gauze screen in the air box. I think way too much air was making the mixture miles off... does that make sense ?

Makes perfect sense i just ordered complete air box with side cover, backfire screen, uni filter, and all pins and bolts for 50 shipped.We shall see if that fixes her. I am still going to try larger main jets to keep the pod filter since i am going to run it only on the street but not if it makes it run like garbage.
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Re: Could use some Help please

Post  Mauser on Wed Sep 07, 2016 7:50 am

Its almost like you have lost all the natural vacuum within the carb so the fuel cannot be draw through, its just too open....you could have wrapped some cloth around the pod filter to restrict it as test but I think your best going down the airbox route listen up

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Re: Could use some Help please

Post  PeteN95 on Wed Sep 07, 2016 6:36 pm

Your SM doesn't still have this installed, does it??

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Re: Could use some Help please

Post  SMXR on Thu Sep 08, 2016 5:57 am

PeteN95 wrote:Your SM doesn't still have this installed, does it??


No sir that was taken out both bikes before i bought them
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Re: Could use some Help please

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