Hotcams valve clearance

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4/13/2018 3:28 AM

Have a question on the specified valve clearance for my hotcams. My bike is an 09 kx450f.

Hotcams specifies .15mm for my exhaust valves. My service manual is .17-.22mm.

There wasnt this kind of conflict on the kx250 i built. Just wondering if anyone else has had this issue and how they dealt with it. Is hotcams spec good? My bike starts in 3 kicks cold and seems to run fine.

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4/13/2018 4:33 AM

Yeah depending on the lift of the cam they call for different clearances. You’re fine running what hot cams reccomends, or at least I always have been

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RPM Performance
CT
783

4/13/2018 4:42 AM

murph783 wrote:

Yeah depending on the lift of the cam they call for different clearances. You’re fine running what hot cams reccomends, or at ...more

Thanks for the input. Do you happen to know of a range of acceptable clearance? Holding exactly .15mm isnt really possible when shims come in standard sizes

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4/13/2018 5:10 AM
Edited Date/Time: 4/13/2018 5:11 AM

I have found over the years that the Hot Cams spec's will work fine if you check your clearances very often, but I have gone back to OEM spec's and have had a lot less issues with maintaining these clearances. I just feel like the Hot Cam spec's are just too tight for the everyday rider and the chance of valve damage is less running the OEM spec's.

Paw Paw

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4/13/2018 5:11 AM

murph783 wrote:

Yeah depending on the lift of the cam they call for different clearances. You’re fine running what hot cams reccomends, or at ...more

kb228 wrote:

Thanks for the input. Do you happen to know of a range of acceptable clearance? Holding exactly .15mm isnt really possible ...more

Well now this is just my personal thought, I don’t know exactly what hot cams says, but I’ll use that as a middle point and allow a couple hundredths on either side. So if you’re using metric call it about .13 to .17mm

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RPM Performance
CT
783

4/13/2018 5:15 AM

murph783 wrote:

Yeah depending on the lift of the cam they call for different clearances. You’re fine running what hot cams reccomends, or at ...more

kb228 wrote:

Thanks for the input. Do you happen to know of a range of acceptable clearance? Holding exactly .15mm isnt really possible ...more

murph783 wrote:

Well now this is just my personal thought, I don’t know exactly what hot cams says, but I’ll use that as a middle point and ...more

Hotcams literally says “valve lash: .15mm”. No range whatsoever.

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4/13/2018 5:27 AM

Paw Paw 271 wrote:

I have found over the years that the Hot Cams spec's will work fine if you check your clearances very often, but I have gone ...more

Youve never had issues with too much clearance?

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4/13/2018 8:04 AM

No issues at all. If the clearance is too tight, even by .001" it can cause valve sealing issues and cause damage.
The intakes are the worst , but the exhaust can do the same thing.

Paw Paw

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4/17/2018 5:04 PM

Anyone notice more noise from the valve train with hotcams?

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4/17/2018 7:36 PM

I have not noticed any extra noise when installed in a rebuilt or new head, but I have with the install of the units in used heads. The reason may be due to valve guide wear, extra lift of the cam causing the valves extending further in the guides as well as the buckets traveling a bit further.

Paw Paw

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4/18/2018 1:35 AM
Edited Date/Time: 4/18/2018 3:10 AM

I installed them in a new head with new valves and springs. My clearance was a little loose than their spec. Went up a shim size on the 3 valves out of spec to tighten them up. Noise is gone but the bike is hard to start & wont idle without some throttle. - sign of valves out of adjustment. Atm im stuck between shim sizes.

Spec on the exhaust cams: .006” and thats the clearance i have.

Spec on intakes is .004” and i have .0035” on both. Going down 1 shim size(.05mm) will give me .006” clearance.

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4/18/2018 5:51 AM

Go loose on the intakes. Your hard starting tells me that they are too tight.
Did you also install a new cam chain?

Paw Paw

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4/18/2018 6:07 AM

Yeah new cam chain too. I checked the tension on it too and it looks good.

Intake clearance from hotcams should be .10mm.
Ill go back to .006”(.15mm) clearance on the intakes and see how that goes. If i still hear noise ill make a video of it

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4/18/2018 3:46 PM

Thought id give an update..

Went ahead and moved the intakes back to .006” clearance. I left the exhaust cams alone after the adjustment from .008 to .006.

Bike runs good. No noises. Ill know for sure on saturday when i ride.

All ive got left now is to rebuild the fuel pump and will be on my way i think. Thanks for the help pawpaw. Always killin it

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4/18/2018 3:52 PM

Good to hear!

Paw Paw

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4/21/2018 5:03 PM

Alrighty.. went and rode today. Probably rode for 20 mins before the intake valves went from .006” to .004” clearance. Ive never seen valves tighten that quick before. What gives? Is that because theyre new? Some kind if break in?

Im going to adjust again and see what happens.

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4/21/2018 6:08 PM
Edited Date/Time: 4/21/2018 6:09 PM

Did you check the clearance with the engine "cold" (like 24 hours without running) or right after it was run. If you did the check while still warm the clearances will be tighter. That is normal and why you have clearances built in. It is also why when they were set too tight why they gave you starting issues. Let it cool for 24 hours and recheck.

Paw Paw

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4/21/2018 7:43 PM

Paw Paw 271 wrote:

Did you check the clearance with the engine "cold" (like 24 hours without running) or right after it was run. If you did the ...more

The engine felt room temp.

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4/21/2018 8:03 PM

Take the shims that were too tight. Get some fine grit sand paper and WD40, place paper on glass or solid surface. Spray WD on paper. Then sand shim down a few thousandths. I’ve done it in a pinch and never had issues.

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Tomac and/or Anderson for 2020.....

4/21/2018 8:14 PM

BobPA wrote:

Take the shims that were too tight. Get some fine grit sand paper and WD40, place paper on glass or solid surface. Spray WD on ...more

X2. I do the same as BobPa to get more exact tolerance

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4/22/2018 5:22 AM

Im chasing a problem i had yesterday with the bike where it was cutting out like it was out of gas. Eventually it didnt start.

I replaced the fuel pump with a spare i had. Intake valves were tight so i adjusted those.

Got the bike running but it only ran woth the high idle knob out.

I think its electrical. Probably coolant temp sensor.

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4/22/2018 7:03 AM

It is a fuel starvation issue.

FYI: Room temp feel is not that same as a good 24 hour cool down.

Paw Paw

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4/22/2018 9:56 AM

Paw Paw 271 wrote:

It is a fuel starvation issue.

FYI: Room temp feel is not that same as a good 24 hour cool down.

Paw Paw

Dirty injector im thinking. Took the old fuel pump apart. Noticed the filter was black and dislodged from the pump. I was able to see sediment.

Too bad harbor freight was out of ultrasonic cleaners

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