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Discussion Starter · #1 ·
I have an 08 kfx450r it has a full dasa exhaust, fci, Dr.d mod box and an accel coil upgrade. I recently added a manual timing chain tensioner and wiseco kx cams and a wiseco chain I got it all back together step by step from my manual topped it off with oil and went to start it and starts very hard when it does start. I had to use the cold start knob pulled out and it finally fired. I rode it for 15 min or so lightly to break in and shut it off and now will not start again. I checked valve clearances they were all to spec. Double checked timing that is all right on. Changed spark plug just in case. Still nothing. I checked the idle air knob backed down all the way counter clockwise and out 22 clicks. I am at a loss curious if someone out there has had similar issues or maybe something I can try. Any input is greatly appreciated.
 

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Ive heared of people putting stock kx cams on the kfx 450r but not wiesco kx cams on a kfx 450r. Might have too much lift or something. I only know so much but others will chime in soon. Good Luck!
 

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I have an 08 kfx450r it has a full dasa exhaust, fci, Dr.d mod box and an accel coil upgrade. I recently added a manual timing chain tensioner and wiseco kx cams and a wiseco chain I got it all back together step by step from my manual topped it off with oil and went to start it and starts very hard when it does start. I had to use the cold start knob pulled out and it finally fired. I rode it for 15 min or so lightly to break in and shut it off and now will not start again. I checked valve clearances they were all to spec. Double checked timing that is all right on. Changed spark plug just in case. Still nothing. I checked the idle air knob backed down all the way counter clockwise and out 22 clicks. I am at a loss curious if someone out there has had similar issues or maybe something I can try. Any input is greatly appreciated.
Make sure the manual cam tensioner is not too tight causing a drag on the motor...!!

Check the decompression spring on the exhaust cam...??

Count 29 pins between the cam's timing marks, one tooth off will cause your symptoms off

see pictures...below
 

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I'm guessing the Dr.D mod box is a three button programmer.

Try setting 4.5, 5.5, 3.5 on your programmer if it's a three button.

Make sure there isn't any vacuum leaks around the throttle body
Check battery voltage.
 

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Discussion Starter · #6 ·
An update I have checked timing it is right on timing marks are even at top of head surface and 29 pins. I changed the mod box to those settings and it started up quickly but after riding it for 15 min and engine warm I shut it off and now won't start again. It almost seems like its a fuel issue.
 

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Graffam64,

I know you said the valves were in spec, do know exactly what the measurements were on the intake and exhaust. Reason I ask is with it starting up fine with the new mod box settings and running for 15 min without issue and then not starting leads me to think the valves are possibly tight. If they are on the low end of the spec for cold valve lash settings I could see them getting tighter as the engine warmed up causing a hard start issue when it's hot. A fuel issue I would think would show up a lot sooner than 15 min into a ride. Then again, if you haven't cleaned the fuel filter in a while it sure wouldn't hurt to pull it and clean it, if nothing else it's piece of mind and you know it's clean.

Have you checked spark when it won't start? Also, is the fuel pump priming when you turn the key on after it's warm and won't start? Does it pop or give any indication that it wants to start after it's warm?

Tony
 

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Discussion Starter · #8 ·
It does pop when it tries to start after its warm. The valve clearances were both intake were .1024mm and the exhaust were .18mm and .20mm. Do they get tighter as the engine is used more with the new cams?
 

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If your intake valves are set right at .10mm for cold lash that is the very bottom end of the spec for the intake. This could possibly be causing your problem. As the engine warms up metal expands, this could be causing your valves to actually be well under the spec once it's warmed up and making your quad really hard to start. The popping also tells me that it's wanting to start. Is the popping coming out of the intake or exhaust? Try setting your valves around .13-.14mm cold lash on the intake and see if that helps. Make sure and do this when the engine is completely cold, i.e. ambient room temp before taking your measurements.

I just went through this on the new motor, had the valves initially set after the motor was in the quad. Noticed that it was harder to start than before the motor rebuild, nothing horrible but it use to start instantly. I checked my valves a little over a week ago and sure enough, my intake was sitting right at .10mm and the exhaust was at .15mm. I reset the valves to the proper spec and she fires right up now.

Tony
 

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Discussion Starter · #10 ·
So when checking the clearances should the feeler gauge slide ride under the lobes or should there be a little drag ? My motor is completely cool. The left side intake is .10mm the right side intake is .13mm. The left exhaust is .20mm and the right exhaust is between .20mm and .23mm
 

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The Intakes always seem to tighten up.

My guy sets them at .14 every time. After 25-30 hours they tighten up to .10

The higher the lift the more they are going to pound into the valve seats and tighten up.
 

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Discussion Starter · #12 ·
I got my intake shims out and,both measure 2.45. How do I correctly do,thr equation to figure out what shim I need now
 

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Discussion Starter · #13 ·
I got both intake shims out and they measure 2.45. The left side was originally a .10 so I replaced the shim with a 2.33. The right side was a .13 so I replaced the 2.45 shim with a 2.38. I got it back together and it still seems to do the same thing. It started good first time rode it around and shut it off and still hard hard starting after that. It ran perfect before I took the stock cams out replaced the chain cams and tensioner and now I cannot get it to start correctly after the first time. I replaced the cams for ice racing here in maine I just wanted to get them in and tuned before winter.
 

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I don't know the measurements on shim sizes.

But as long as you get .14 cold your good.

Why did you use a manual tensioner? The oem is great.

Some of your problem could be from the tensioner too
 

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The 2.45 on the shim is the thickness of the shim itself in (mm) millimeters. Going from a 2.45 mm shim to say a 2.50mm shim would put your lifter bucket .05mm closer to your cam lobe, i.e. it would go from .15mm clearance to .10mm. By taking the 2.45 shim out and replacing it with the 2.33 shim you opened up the clearance from .10mm to .22mm. You may want to replace that 2.33 shim with a 2.40 shim instead, this should put the one intake lobe that was at .10mm right at .15mm. The side that was already at .13mm you probably could have left alone and been alright. With the shim you put in there you opened up the gap on that lifter bucket from .13mm to .20mm.

I agree with blue99stroker about the OEM cam chain tensioner, it's a good unit and self adjusts. You also may have the manual tensioner to tight as blue99stroker also mentioned.

If you have a set of calipers you can measure the shims if you are unsure of the size. Use a millimeter to inch conversion to get the actual thickness in millimeters.

Hope that helps

Tony
 

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Discussion Starter · #16 ·
I was told by a few people the manuals are better but i am going to put the stock one back in and try that. If that doesn't work in going to put the stock cams back in and try that. I'm running out of things to try. Thanx again for the help and info so far fellas
 

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I would get the cams adjusted to spec like coop said.

Then swap the tensioner if that still doesn't fix it.
 

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Discussion Starter · #18 ·
I'm going to redo the shims today. I did pull the plug and the end seems like its whiter then normal
 

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I got both intake shims out and they measure 2.45. The left side was originally a .10 so I replaced the shim with a 2.33. The right side was a .13 so I replaced the 2.45 shim with a 2.38. I got it back together and it still seems to do the same thing. It started good first time rode it around and shut it off and still hard hard starting after that. It ran perfect before I took the stock cams out replaced the chain cams and tensioner and now I cannot get it to start correctly after the first time. I replaced the cams for ice racing here in maine I just wanted to get them in and tuned before winter.
Your valves are still the problem...Re-check the valve clearance...And Don't guess at it, you'll make it worse

Get yourself a Digital caliper and Bikemaster feeler gauges
BikeMaster 12-Blade Combination Tappet and Feeler Gauge Set 173146

150mm / 6inch LCD Digital Electronic Gauge Steel Vernier Caliper Ruler Stainless | eBay

Valve Clearance: between cam and valve lifter
Standard:
Exhaust 0.17 ∼ 0.22 mm (0.0067 ∼ 0.0087 in.)
Inlet 0.10 ∼ 0.15 mm (0.0039 ∼ 0.0059 in.)

Your Intake at 0.10mm is now 0.22mm...2.45 - 2.33 = 0.12mm...you only need 0.04mm to put them at 0.14mm clearance...???

Your intake at 0.13mm is good...But now it way off...2.45 - 2.38 = 0.07mm..It's now at 0.21mm..

Both intake valves are out of range and barley opening...So now your motor is starved for fuel/air...

Intake at 0.10mm you'll need an 2.40mm shim to put them at 0.15mm...!

Intake at 0.13mm is good..Put the 2.45 shim back..or a 2.44mm shim to put them at 0.14mm...
 

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Discussion Starter · #20 ·
I reinstalled the stock tensioner got the valve clearances at .13 and .14. Everything retimed back at 29 pins. Started kinda shitty again but started ran it for 10-15 shut it off and same thing. Poping thru exhaust and just about kills the battery trying to start it again. I keep a battery maintainer on it all the time. I'm at a loss. Thinking i may have to reinstall the stock cams just to kill my curiosity. Anything else i should try first?
 
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