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Well the chain is not the problem, but it is the wrong chain to use. Internet sellers promote the CRF450 chain as HIGH PERFORMANCE and it's cheaper. It is cheaper because it is made of lighter materials. The CRF is a race engine and as a cost of racing the chain is expected to be replaced frequently. It is the same length, but it is wider than the heavier TRX chain so it will walk from side to side and eat the guide rails off side the tensioner. But, it will run with it.

Now the one thing you did wrong was setting TDC - TDC is the T mark on the flywheel - the marks ahead of the T mark are the ignition full advance marks - if you lined up the advance marks, the the cam is about 2 teeth out of time and you could easily bend the valves if you cranked the engine with the electric starter. I always turn the engine by hand to 'feel' contact if the valves touch the piston. This is critical when building race engines.

Now if the marks ahead of the T mark line up in the timing port when the piston is at TDC, then the flywheel key is sheared and needs to be replaced as well.

Let me know what you come up with. I'm getting off line for the night and will check back tomorrow morning. I don't have a SMART phone as I don't trust the technology. Computers are just as bad, but at least Google does not own the operating system and I can choose browsers and search engines. Try installing Mozilla on a smart phone and then try getting Swiss Cows as a default search engine. I don't think Google's Android operating system will allow it.
 

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Discussion Starter · #22 ·
The mark in front of the”t” that I lined it up with is right before the “t” and after the “f”. It basically is the “t” maybe just a hair off. I can send a picture tomorrow of what I mean.
 

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Discussion Starter · #23 ·
Would the flywheel key shear off without me messing with it at all? I took the top apart again and the timing is still on. The “t” with the line in front of it is lines up with the mark on the crankcase. And the cam looks the same as it did in the video I sent in. I also have the clutch case removed to see if I messed anything up but I don’t see any issues there. Could I have messed up the timing from the crankshaft when I switch the chain out?
 

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If the T mark (not the T itself) is aligned in the inspection hole when the piston is at TDC, then the flywheel key is fine - no, you can't mess up the timing on the crankshaft - the cam turns at 1/2 the speed of the crankshaft and there is no being off by 180 degrees - as long as the piston is at TDC when the cam is installed (lobes up or down) makes no difference, but if the lobes are pointed up, it makes installation of the head cover more difficult. You need to investigate the no compression issue.
 

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Discussion Starter · #25 ·
Ok, I'm going to get a better air gun nozzle so I can easily push air through the engine to see where it is coming out. When I replaced the valves I did see that the intake valves were bent. and I'm guessing the new ones are bent as well. If they are bent that means I have an issue causing this every time I try to start it. The only thing I can think that would cause it is timing as it has a new piston and rings and gaskets all around. I'll take pictures of the timing and upload them, to verify I am correct and not crazy. I'll probably reply tomorrow as I don't have time in the evening to work on it, unfortunately. so I am waking up earlier in the morning to work on it an hour before work. Again thanks for all the help.
 

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Discussion Starter · #27 ·
So there was resistance when I turned it over by hand yesterday. I put the head back on and attached the timing chain to the sprocket and when I turned it over by hand it got stuck, then I turned it clockwise then back counter-clockwise and the resistance went away. It did feel a lot harder to turn over by hand this time. I have to wait for the new valve to reassemble. while I wait I took the clutch case off this morning just to verify I didn't mess anything up. I did notice the timing chain is somewhat loose on the crank sprocket. But I'm guessing that is ok. Everything else looks normal and I didn't see any shavings or other issues. What have you seen in the past that would cause the resistance issue.
 

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If the head is on, spark plug out valves closed and cam chain off (removed from the crank); the only resistance to movement is: in the CCW direction (normal direction of crankshaft rotation as viewed from the LH side) is the magnets in the flywheel attracted to the laminated poles of the stator. In CW rotation, the starter motor is turned in reverse and provides a constant resistance.

Since the engine was worked on previously, did you assure the piston was installed in the correct orientation?

You used a CRF450 cam chain, so it is too wide for the sprockets and there will be some movement or slop in it even when the tensioner is installed.

What have I seen that will cause a resistance issue? Cam chain tensioner installed incorrectly, valve timing wrong, rocker arm issue in a Niche head cover, bad crank main bearing, bad lower rod bearing, bolt holding starter clutch to the flywheel backed out and contacting the stator, chip of aluminum wedged between two teeth of the crank pinion gear, counter balancer 1 tooth out of time and striking the bottom of the rod (not hard enough to do damage, but caused resistance to rotation in the same spot of each rotation and caused a knock that sounded exactly like a loose rod even with a stethoscope, broken or otherwise damaged valve guide, incorrectly installed ring, stretched rod, incorrect head gasket, head cover installed without the shim/gasket, defective cam chain, damaged cam chain sprocket, incorrect bolts in the cam sprocket, cam chain tensioner installed incorrectly at it's pivot point, a cylinder bored improperly and was tapered smaller on the top than at the bottom causing the ring end gap to close and the rings bind at the top of the stroke............ I'm sure there have been other causes, but that is the bulk of them and when working on something that someone else has worked on, you have to check everything. I trust my work, but not others and even those who I trained, but did not have the ability to teach themselves. They may have a reputation for doing good work, but I invariably get to correct their mistakes.

The mechanic who taught me how to build engines watched me build a race engine and commented that I could build better motors than most, but I also know there is someone who can build better motors than me.

The key is attention to detail and a keen sense of observation. If you want the cam timing perfect, you need to install a degree wheel on the crank, slot the bolt holes on the cam sprocket, and set the valve timing with a dial indicator.

I can tell you this: the engine will run fine with the cam a full one tooth off, but one way it is harder to start and runs like a raped ape, the other way is is easy to start, but lacks power when WFO (wound flat out).
 

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Discussion Starter · #29 ·
Wow, that is a lot of issues you have worked through. So I recalled a post you made a few months ago for someone else that was having an issue.

in the post you said " Lock the crankshaft at TDC of the compression stroke, install an adapter into the spark plug and using compressed air, slowly put air in the cylinder increasing the pressure up to 150 psi. If the valves are bent, you will detect air exiting the combustion chamber through the intake, exhaust, or both before you get more than 30psi into the cylinder "

I'm more of a parts changer and not really a mechanic, with that being said. How can you tell when the piston is at TDC on the compression stroke. I know when the piston is at TDC but not if it's on compression or exhaust.

Just to ensure I did the valves correctly. I used a shim that was .10mm on intake and .12mm on the exhaust. and adjusted them down to wear they grab but don't pinch the shim.
 

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The piston is at TDC of the compression stroke after the intake valve closes: it's piston downward on the power stroke, upward on the exhaust stroke, downward on the intake stroke, and upward on the compression stroke where spark happens just before TDC. TDC of the exhaust stroke has both valves open a bit.

The valve sequence is (starting at TDC of the compression stroke): at about 160 degrees after TDC, the exhaust valve starts to open, the piston reaches BDC (bottom dead center) and the exhaust valve is fully open about 20 degrees after BDC , the piston is traveling up and pushing out spent mixture as the exhaust valve is closing - at about 20 degrees before TDC the intake valve starts to open - during about the next 15 degrees both the intake and exhaust valves are open (this is referred to as overlap) - at about 20 degrees after TDC, the exhaust valve is fully closed and at about 150 degrees after TDC the intake is fully open and starts closing at about 160 degrees after TDC - the intake valve is completely closed at about 110 degrees before TDC and the piston is traveling up on the compression stroke - at about 15 degrees before TDC, spark occurs to start the combustion process - the piston goes past TDC on the power stroke and the cycle repeats.

Now people put too much emphasis on valve clearance. Too loose is better than too tight - I work in thousandths of an inch - .003 intake and .005 exhaust which is .10mm and .12mm - perfect is where you can feel drag, but can reinsert without pressure. I uses the go no go method - if a .003 goes and a .004 does not, it's perfect and if a .005 goes, but a .006 doesn't, it's done - .10 goes and .12 does not, intake is good - .12 goes and .14 or .15 does not, exhaust is good. You are allowed + - .001" and .01mm so 2 to 4 intake and 4 to 6 exhaust. It's not that critical. You can run less than zero clearance and not notice much of a difference other than hard to start. You can run .010 and .012" (what my CRF specifies) and not hear any tappet rattle, so just assure a bit of free play between the tappet and the valve and it's good for starting.
 

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Discussion Starter · #31 ·
I checked the valves yesterday and they were completely off. The intake valves wouldn't even fit a .002 and the exhaust valves fit a .009. I had it at TDC but am not sure if it was on the compression stroke. Does that make a difference? Also, the valves could be bent again so I'm not sure if that would make the difference. I adjusted them before to fit in spec, so I'm kind of confused as to why they are off now.

Also, I did notice that the crankcase cover has gasket maker on it. I didn't mess with anything in the crankcase so I guess there could be a possibility the last person didn't tighten the bolt down enough for the flywheel. But it did run for a while before anything happened though so I am not sure if that's it.
 

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An insufficiently torqued flywheel can shear a key and still be tight which will throw the TDC mark off when the piston is at TDC and it will run for a good while before the key will shear.

To know that you are on TDC of the compression stroke (and yes it makes a huge difference whether you adjust the valves on TDC of the compression or exhaust stroke) - turn the crankshaft CCW - when the intake valve closes and the piston reaches TDC, you check and adjust the valves. Check the position of the piston through the spark plug hole.
 

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Discussion Starter · #33 ·
Thanks for all the help. I finally got it to start! I adjusted the valved on TDC of the exhaust stroke. I did fix it and adjusted them on the compression stroke.

I still have a pretty loud rattle and am not sure if it's valves or the timing chain. Do the 400ex usually have a ticking noise?

Also, it is running pretty rough and was hard to start ( the choke is broke so that could be why it was hard) I did put the Niche stage 1 cam in it, do you think I need to change anything in the carburetor. The carb is an ebay carb and I was thinking about replacing it with another because of the broken choke.
 

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A tick in a 400 is not abnormal unless it gets louder - my 400 ticked from day one and never changed.

I would do my best to try to find an OEM carb (it was either Mikuni or Keihin and I believe it was a Mikuni) and rebuild it if needed - there is no way I would put a Chinese carb on it as you can't get parts for them - you can buy replacement choke parts for the OEM carb, but they would cost about as much as a whole Chinese POS counterfeit carb.

Good luck and glad to hear you got it running.
 

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Discussion Starter · #35 ·
Hello,

I figured out it is a keihin carb and I fixed the choke issue. The quad is very hard to start and I think it might be an issue with jetting. I ride around 650-1500 elevation, It has a hmf slip on, a stage 1 cam and I plan to do an air box mod as well as second oil cooler or larger oil tank. Do you have any suggestions on jetting ?
I believe the previous owner installed an incorrect throttle cable for the carb, the cable doesn’t thread into the top of the carb and it has a gap between the throttle and carb and is sloppily sitting in the carb. Im not sure if that would cause an issue with starting but the throttle seems to move fine. Hopefully I can find the correct part number and it works out.
 

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I can't advise on jetting as I have no idea what type carb or current jetting - is the carb an FCR, CV or round slide style? What size is the venturi? The cam and engine work does not affect jetting, but the exhaust does slightly and changes to the intake affect jetting the most. It's the responsibility of the engine builder to jet the carb for the changes and if the venturi of the carb is larger than the original carb, the jets have to be decreased in size whereas if the venturi is smaller, the jets have to be increased in size over standard for the original carb. Removing the top from the air box requires changes to all fuel circuits in the carb (idle, mid-range and wide open throttle). Starting is primarily compression and ignition - too little fuel makes for hard starting and too much fuel can be a problem too, but too much can be compensated for with an increase in throttle opening.
 
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