Cam chain timing (400ex) - Honda ATV Forum
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post #1 of 9 (permalink) Old 01-16-2013, 08:10 PM Thread Starter
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Cam chain timing (400ex)

I picked up a 2005 400ex for cheap because it didn't run, no compression. Ended up being a cracked valve seat. Sent the jug and head out, put it back together with a new weisco 11:1 piston and a white brothers WB1498 cam off ebay. Also rebuilt the carb. During the rebuild, the cam chain was very slack and rattled around in the crankcase freely (more on this later). i put the whole thing back together, and noticed during the cam install that the timing lines were just a little off of square from the top of the head. Didn't think too much of it, put it all back together, and now it wont run...

I am running a full air box with snorkel, k&n, and a new FMF powercore4. Jetted at 165/42, 3 turns out. No adjustable needle

If i hit the accelerator pump before cranking a couple times, i can get it to sputter, and if i hit the throttle just right, i can get it to run, just not idle, it immediately dies, but if i hold it, it will stay running high, so it is drawing a vacuum properly from what i can tell

So after reading and reading, i decided a stage1 hotcam is going to better suit my terrain (tighter woods), so i have the cam torn out, and was wondering if the cam chain can skip a tooth on the crank to affect timing? Or did i just adjust my valves wrong?

Open to any ideas, i can grab a shot of the cam timing mark if that could be useful

Halp!
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post #2 of 9 (permalink) Old 01-17-2013, 04:30 AM
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Welcome to the forums. . . .YOu did install the cam lobes down correct??what I normally do it set the dash mark closest to the timing tensioner or back of the engine a little higher than the head surface maybe 1/16-1/8th so when you snap the tensioner back to it's working position it will pull the chain tight and the cam right where it needs to be. check your cam sheet for the valve lash specs and set it to them. What are you going to do with the White brothers cam? might have a buyer if the price is right???

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post #3 of 9 (permalink) Old 01-17-2013, 01:12 PM Thread Starter
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yes, lobes down. so you don't think 1 or 2mm difference on the timing tics is enough to throw it off? I'll re-do the valves for the new cap specs. i was thinking the cam lines would have been perfectly parallel to the top of the motor

cam is for sale, let me know what you think the right price is...
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post #4 of 9 (permalink) Old 01-17-2013, 01:44 PM
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Check your valve clearance again. They may be to tight. .

"MOOSE WAGON "
00 TRX400EX aka "MOOSE ROCKET"
91 TRX250X aka "MOOSE WAGON" RETIRED
96 Polaris 400L sport (Mrs. Moose Ride)
07 Suzuki LTZ250 (Sons)
96 Polaris 250 Trail Blazer (daughters)
06 TRX450ER aka === Under construction

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PM FOR MANUAL HELP
JETTING
Service_Manual_Downloads
2000_400EX_Build
400EX_Pivot_Bolt_
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post #5 of 9 (permalink) Old 01-17-2013, 01:54 PM
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If the chain has any slack with the tensioner installed,replace the chain now,then set the cam up with the new chains slack on the tensioner side,install the tensioner,and check the alignment marks,if off a tooth,remove the tensioner,and back the cam up a tooth,reinstall tensioner...then rotate the engine by hand ,and check the timing marks again,if the lobes are down,the t marks aligned,and the cam marks are dead on then it is right ...

FREE REPAIR MANUALS >>http://www.hondaatvforums.net/forums...all-years.html 1986-1992 trx350 parts for sale>>http://www.hondaatvforums.net/forums/atv-parts-sale/29225-complete-part-out-1986-fourtrax-350-a.html
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post #6 of 9 (permalink) Old 01-17-2013, 02:56 PM
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If you need to replace the chain, be sure to use a CRF450 timing chain, part# 14401-MEB-671. It is a much stronger chain and about half the price of a 400EX chain.

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post #7 of 9 (permalink) Old 01-17-2013, 08:20 PM Thread Starter
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Ok! Sage 1 cam in and timed the same ever so slightly off as the wb cam. Pulled the plug during the timing portion to relieve compression, and noticed that the gap was extremely tight. New plug, gapped properly. Adjusted the valves and originally made the idiot mistake of .15" instead of .15mm. Threw the whole thing together, and it sputtered a bit more than i was used to and eventually got it running, then idling! It is in the 30's tonight so i bet she was a little cold, hence the hesitation. Didn't let it idle too long as i want to break in the cam and engine properly, so i need some good variation etc. threw the skins on it, ready for tomorrow!

TL;DR: plug gap and the difference between inches and mm for valve adjustment

And that WB cam is still up for grabs if you know anyone. Ill even throw in the hogged out sprocket (for advanced timing) that i got with it

Thanks everyone!
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post #8 of 9 (permalink) Old 01-17-2013, 09:30 PM
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You can post an ad for the cam in the for sale section on the main page(click atv forum up top),then scroll down to the bottom..

FREE REPAIR MANUALS >>http://www.hondaatvforums.net/forums...all-years.html 1986-1992 trx350 parts for sale>>http://www.hondaatvforums.net/forums/atv-parts-sale/29225-complete-part-out-1986-fourtrax-350-a.html
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post #9 of 9 (permalink) Old 01-18-2013, 04:08 AM
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Glad you got it going

"MOOSE WAGON "
00 TRX400EX aka "MOOSE ROCKET"
91 TRX250X aka "MOOSE WAGON" RETIRED
96 Polaris 400L sport (Mrs. Moose Ride)
07 Suzuki LTZ250 (Sons)
96 Polaris 250 Trail Blazer (daughters)
06 TRX450ER aka === Under construction

Progress and Help
PM FOR MANUAL HELP
JETTING
Service_Manual_Downloads
2000_400EX_Build
400EX_Pivot_Bolt_
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