Backfiring----Valves???????

**Kenny4** · 02-06-2010, 04:16 PM

Ever since I put the Yoshi duals on, it's been backfiring on decel under load in all ranges---Have played with a/f screw changed jetting up and down---Have never been able to fix it---It starts good and runs strong---I did find some leaks in the exhaust connections but way back by muffler.

Can't get to the leaks so I just pulled off the whole system and put on another brand new set of duals---Pro Circuits---And crap---It backfires worse with them on and there is no exhaust leak anywhere.

The only 2 things I haven't looked at is the pilots to see if they are dirty or clogged or checked valve clearance---I've held off on the valves as so many have posted up what a bucket of worms they opened---Actually R&R'ing the the air filter box is for some reason more intimidating to me than the valves.

If you guys have any other suggestions please post up---I'm sure if I mess with the valves I'll be back on here whining about something

Kenny

**Camo** · 02-06-2010, 04:46 PM

How many turns out are your fuel screws?

**Kenny4** · 02-06-2010, 05:33 PM

Quote: Originally Posted by Camo

How many turns out are your fuel screws?

They are 3 turns out

**Toyotadude** · 02-06-2010, 08:24 PM

I'd check the valves anyway if you feel you can just to eliminate one more thing.

Nathan · 02-06-2010, 10:17 PM

I had the same issue I got 42 pilots and was able to tune it out now I never have any popping.

lambosr82 · 02-08-2010, 03:40 PM

Had same issue when I put my HMF's on changed out the pilots to 42's fixed the issue

NovaKaw650 · 02-08-2010, 04:03 PM

It's probably lean and needs bigger pilots as others have pointed out, but check the valve clearance anyway. It's part of scheduled maintenance and needs to be done.

**Kenny4** · 02-10-2010, 05:58 PM

Appreciate the posts---If I change out the pilots from #40's to #42's, (most of the threads recommend this when UPP's are added but not for stock), if it's too much/too rich how will I know in the seat---What should be a good indicator that it needs to go back to #40's.

Today is Wedn. and I might be leaving tomorrow nite to do about 150 miles of riding---I don't want to do anything that will screw it up---As it starts fine and runs well except for constantly backing off on decel---I love the rumbling sound of it but can't be any good for it to run this way---Also the rear exhaust has been showing black carbon/soot lately, (at 182/185)--I don't have any other jets, but was thinking of trying to change the front to the rear, (185/182), just to see if it does anything noticable.

When I get back will definitely look at valve clearance too---Thanks

Kenny

02-06-2010, 04:16 PM	#1
Kenny4 Premium Member Feedback Score: 0 reviews Join Date: Dec 2008 Location: Southern, California Posts: 1,116 (9)	Backfiring----Valves??????? Ever since I put the Yoshi duals on, it's been backfiring on decel under load in all ranges---Have played with a/f screw changed jetting up and down---Have never been able to fix it---It starts good and runs strong---I did find some leaks in the exhaust connections but way back by muffler. Can't get to the leaks so I just pulled off the whole system and put on another brand new set of duals---Pro Circuits---And crap---It backfires worse with them on and there is no exhaust leak anywhere. The only 2 things I haven't looked at is the pilots to see if they are dirty or clogged or checked valve clearance---I've held off on the valves as so many have posted up what a bucket of worms they opened---Actually R&R'ing the the air filter box is for some reason more intimidating to me than the valves. If you guys have any other suggestions please post up---I'm sure if I mess with the valves I'll be back on here whining about something Kenny __________________ "As For Me And My House We Shall Serve The Lord" 2007 KFX 700 V Force------"DIY MODS"-----Pink Spring---Yoshimura Duals---12 Hole Mod---Twin Air Power Kit---1 Shim & Cut Springs---Polished Slides--- 3.0 turns out---#40 Pilots---182F/185R---Spark Plug Boot Mod-----------"OTHER STUFF"---Odi grips---Full Under Armor---Billet Stator Cover---HID Lights---Trail Tech Vapor---Pro Armor Front Bumper---Rear 6 Pack Rack---Nerfs--22x11x10 Haulers 10 Paddle---22x11x10 Edges 9 Paddle---Quick Release Lighted Whip---IMS 4.6 Gas Tank 2005 Honda Rancher 350ES The Avatar picture is my custom home for sale in Yucca Valley, So. Calif.

02-06-2010, 04:46 PM	#2
Camo Super Moderator Feedback Score: 14 reviews Join Date: Dec 2004 Location: Canada eh! Posts: 16,816 (0)	How many turns out are your fuel screws? __________________ OrangeCrush RR Boosted / Nitrous Injected Duner Fundy Performance Sports 1-902-893-(DYNO) 3966 1) Bench Racers 2) Racers who never actually run into the Big Dog 3) Racers who win everything until they meet up with the Big Dog 4) The Big Dog CUSTOM FABRICATED TURBO EXHAUST JH MACHINE CUSTOM ROLLER CLUTCH

02-06-2010, 05:33 PM	#3
Kenny4 Premium Member Feedback Score: 0 reviews Join Date: Dec 2008 Location: Southern, California Posts: 1,116 (9)	Quote: Originally Posted by Camo How many turns out are your fuel screws? They are 3 turns out __________________ "As For Me And My House We Shall Serve The Lord" 2007 KFX 700 V Force------"DIY MODS"-----Pink Spring---Yoshimura Duals---12 Hole Mod---Twin Air Power Kit---1 Shim & Cut Springs---Polished Slides--- 3.0 turns out---#40 Pilots---182F/185R---Spark Plug Boot Mod-----------"OTHER STUFF"---Odi grips---Full Under Armor---Billet Stator Cover---HID Lights---Trail Tech Vapor---Pro Armor Front Bumper---Rear 6 Pack Rack---Nerfs--22x11x10 Haulers 10 Paddle---22x11x10 Edges 9 Paddle---Quick Release Lighted Whip---IMS 4.6 Gas Tank 2005 Honda Rancher 350ES The Avatar picture is my custom home for sale in Yucca Valley, So. Calif.

02-06-2010, 10:17 PM	#5
Nathan Senior Member Feedback Score: 0 reviews Join Date: Apr 2009 Posts: 107 (0)	I had the same issue I got 42 pilots and was able to tune it out now I never have any popping. __________________ 04 kfx 700 orange 12 hole, PRO circuit exhaust, EPI maroon spring, 24" haulers, 6 degree key, UPP intake, 188f 185r 42 pilots 98 polaris scrambler 400 4X4 for sale soon $$$

02-08-2010, 04:03 PM	#7
NovaKaw650 Senior Member Feedback Score: 2 reviews Join Date: Sep 2004 Location: Nova Scotia, Canada Posts: 2,198 (0)	It's probably lean and needs bigger pilots as others have pointed out, but check the valve clearance anyway. It's part of scheduled maintenance and needs to be done. __________________ 2002 665 FPS Prairie FPS Trail kit - 12:1 comp due to 1mm shaved off the heads Mild porting Crossover intakes Modded airbox Full Muzzy Dalton springs and weights Other stuff

02-06-2010, 08:24 PM	#4
Toyotadude Premium Member Feedback Score: 1 reviews Join Date: Oct 2009 Location: Las Vegas, Nv Posts: 203 (0)	I'd check the valves anyway if you feel you can just to eliminate one more thing. __________________ 04 KFX700, HMF Duals, Dynatek CDI, #42 pilots, American Star Racing 2" extended A-arms, G-Force Honda 400EX extended rear hubs, 22-7-10 Sand Stars in front, 24-11-10 8 paddle Extremes in Rear, K&N air filter, AC Nerfs & Six pack rack 86 Toyota 4X4, 4.3L Chevy V-6, 700R-4 trans, Marlin Crawler dual transfer case, limited-slip front diff, ARB rear diff, custom flatbed w/aluminum diamond plate insert, Super Swampers for trails & Desert Trac paddles for sand

02-08-2010, 03:40 PM	#6
lambosr82 Junior Member Feedback Score: 0 reviews Join Date: Feb 2007 Location: Omaha, NE Posts: 17 (0)	Had same issue when I put my HMF's on changed out the pilots to 42's fixed the issue

02-10-2010, 05:58 PM	#8
Kenny4 Premium Member Feedback Score: 0 reviews Join Date: Dec 2008 Location: Southern, California Posts: 1,116 (9)	Appreciate the posts---If I change out the pilots from #40's to #42's, (most of the threads recommend this when UPP's are added but not for stock), if it's too much/too rich how will I know in the seat---What should be a good indicator that it needs to go back to #40's. Today is Wedn. and I might be leaving tomorrow nite to do about 150 miles of riding---I don't want to do anything that will screw it up---As it starts fine and runs well except for constantly backing off on decel---I love the rumbling sound of it but can't be any good for it to run this way---Also the rear exhaust has been showing black carbon/soot lately, (at 182/185)--I don't have any other jets, but was thinking of trying to change the front to the rear, (185/182), just to see if it does anything noticable. When I get back will definitely look at valve clearance too---Thanks Kenny __________________ "As For Me And My House We Shall Serve The Lord" 2007 KFX 700 V Force------"DIY MODS"-----Pink Spring---Yoshimura Duals---12 Hole Mod---Twin Air Power Kit---1 Shim & Cut Springs---Polished Slides--- 3.0 turns out---#40 Pilots---182F/185R---Spark Plug Boot Mod-----------"OTHER STUFF"---Odi grips---Full Under Armor---Billet Stator Cover---HID Lights---Trail Tech Vapor---Pro Armor Front Bumper---Rear 6 Pack Rack---Nerfs--22x11x10 Haulers 10 Paddle---22x11x10 Edges 9 Paddle---Quick Release Lighted Whip---IMS 4.6 Gas Tank 2005 Honda Rancher 350ES The Avatar picture is my custom home for sale in Yucca Valley, So. Calif.

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