Installing cam

[Spikers400]

Me and my friend Hcr400ex just rebuilt his quad. But we are having some problems. It took a little time to get it started, and when it started it did not want to idle(possibly due to the replacement of his idle screw). But if he kept it above idle it ran good, and strong.
That was last night, now today it will not start, there is spark and gas, but it just wont start up. We thought it might have been jetting, so we changed it around, the plug keeps getting soaked. After a few min of messing around on it it backfired 2 times.

My question is would improper instalation of the cam cause it not to want to start? Would it run strong once it was started if the cam was in wrong?

I know we alligned the cam marks right because i have done it before, but one thing i am not sure of is if we put it on on the correct TDC. Would it run at all if it was installed on the wrong tdc, wouldnt that mean it would be trying to start on the ghost spark? Meaning it would be a lot harder?

How can i make sure it is at True TDC when i install the cam?

Thanks,
Ryan

[da400hon]

did you adjust the valves? When you put a higher stage cam in you have to adjust the valves.

[cals400ex]

alighn the T up on the flywheel. when the T is aligned, look at the cam sprocket. either the cam lobes will be facing up or down. when the cam lobes are facing down, all 3 marks on the cam sprocket should be seen. 2 should align with the head and the other should just be facing up. rotate the flywheel 360 degreee (one full rotation) and you will see that the cam lobes are now facing up and you will only be able to see the 2 marks on the cam sprocket that are supposed to align with the head. just remember, the 2 marks need to align with the head with the cam lobes down, the T is aligned up, and the 3rd mark on the sprocket should be facing up.

[Spikers400]

Ok well then im pretty sure i put the cam in the right. It was on tdc, the one line was up and the other two were alligned with the head. I did this all with the tensioner on, so i dont think it would be off a tooth or anything. What else would cause it to be so difficult to start. And the back fire? It must be the jetting right? Also it has been exceptionally cold here the past few days, upper 20s. I bet that has something to do with it.

[Spikers400]

And yes, i did adjust the valves.

[Dalex]

just a reminder , you also have to make sure you put the sprocket side cam ball bearing in correctly with the seal turned out so it can seal the oil galley properly.:D

[Spikers400]

Is that crucial? I really dont remember what he did.
we checked the cam though, and it was ligning up perfectly, so its not timing. We swapped carbs and it still wouldnt run

It has to be electrical. What could be faulty, it is getting spark but possibly not a strong enough spark. I remeber one time my terminal was crapped up and i had to bump start it and it would not idle. What would let it turn over but not give it a strong spark? Possibly stator, or cdi?

Thanks

[Spikers400]

Anyone know? If that seal being on the outside makes a difference?

[440ex2001]

I think you must have it set to tdc on the exhaust stoke. That would explain the back fire and no starting. How did you intall the cam with the tentioner on? You must be a wizard or something. Just take the valve cover off, take the tenioner off , take the timing chain back off make sure your cam lobes are pointing down the lines on your cam gear are right and your flywheel is on the T mark then put the chain back on and then the tenioner double check your timing marks and it should work. If you have spark AND fuel it has to be your timing what else could it be? Are you sure you have spark? Did you use a spark checker? It'll only take an hour or to re-check everything.

[khen]

If your cam turns out to be installed correctly, you might want to put a fresh charge on the battery, or try jumping it.. Does the quad have an aftermarket CDI? Mine did the same thing you are discribing when my battery wasn't at a full charge.

[MIKE400EX]

If the seal is not on the outside then the oil may not get forced thru the cam to all of the lobes/rockers etc... It needs to be on the outside, any place else is inviting failure.
You could loosen up all the head cover bolts enough to pop it up and (a flashlight helps) look into the side by the cam sprocket. If you can see the seal then it's on the outside/correct side.

[Spikers400]

we put the cam and sproket on them put on the tensioner to make sure that there was no slack that could be causing to to be off a tooth. The cam is ligning up when i put it at tdc. I am possitive we put the cam in right.

But it wouldnt idle. What can cause in inseficient spark? It wont even start when the charger is hooked on it, so i know its not the battery.

I am running out of ideas.

[MIKE400EX]

Did you check the alignment marks AFTER you installed the tensioner?

[Rico]

Originally posted by MIKE400EX
Did you check the alignment marks AFTER you installed the tensioner?

Exactly.

It's a good idea to turn the motor over several times to see if the mark lines back up each time adn that your on the compression stroke, which is very easy to miss...:o

[Spikers400]

Ok when i put it on TDC the cam marks lign up. One up and the two side marks are fine.

what i wanna know is what if i were to take the came off rotate the flywheel 360 degrees back to TDC and put the cam in. Would that make a difference? is it possible to install the cam on the wrong top dead center. Or is the true top dead center determined by the cam possition after it is installed?

[Spikers400]

And yes i installed the cam +sproket+ chain. To where i thought it should be. THEN i put the tensioner on to eliminate slack that could possibly be causing the marks to off.

[440ex2001]

OKay, the way that you make sure that it is at the TDC is to make sure that the flywheel is lined up on the T in the inspection hole. Most of the time you would rotate it to TDC and check to see if all the rocker arms are loose that would let you know that your on TDC on the right stroke. You cant really do that now cause things have been moved around. The timing is dictated by the your capacitor discharge ignition (CDI) and trigger on the fly wheel. You need to get the right TDC becasue if you the trigger on the fly wheel which is insync with the rod and piston sends .5v's to the CDI to send voltage to your coil and then spark plug on the wrong TDC (exhaust stroke) 2 valves will be open and its gonna back fire and not run if it does it will be very rough. Unless you get spark on all 4 cycles (intake,compression,power,and exhaust) I would think you need to make sure that you have it on the correct TDC so the ignition fires when all the valves are closed. Just rotate the engine again and then line everything up. It cant hurt to try. I also think you should get a spark checker and check for adequate spark it should be a nice blue charge not red or pinkinsh that indicates weak spark. Just take your time and use a systematic approach to this problem. Its either fuel or spark. Figure out which one it is for sure then chase the problem down.

[MIKE400EX]

The ignition fires once for every revoultion of the crank on these - just like on a 2 stroke. The spark on the exhaust stroke is "lost" on 4 strokes.

[440ex2001]

oh well, disregard everything I just said then :)

[Spikers400]

haha so wait, could it be installed on the "wrong"tdc? Or not?

[sickmojave]

I would do a compression test ;)

[motoboy66]

make sure you used the"t" mark, and not the other s. The "F" looks very much the same, and is very close to the "T". Also you do not put the tensioner on. turn your engine CC until the "T" mark is lined up. Then pull the can chain tight from the front of th engine. Line up the marks on the cam gear with the head. Install the top allen bolt, then while holding the chain, slowly turn the engine over CC until you can put the other allen bolt in. Now you are ready to put the tenntioner back in. If you installed i with the tenntioner, it will throw off the cam timing one tooth. Learne this the hard way, did the exact same thing yours did. This would be my bet for the money. As for the seal on the bearing, they go to the outside. Thats how the manual shows them.

[Spikers400]

I dont know, maby it just needs sum starting fluid, or a bump start. This is not he first engine iv done, the first one went together really smooths and started right up, but it also was a lot warmer out. I have a feelign that is part of the problem.

I dont know where u guys got the fact that i put the tensioner on before the chain. Obviously thats impossible. I put the sproket in the chain then the sproket and chain up onto the cam. Then i put the tensioner on.

The marks line up fine, no way it is off a tooth. It is DEFINATLY not a timing problem.

Idk what to do next. Ill just keep going over it, any other ideas, just let me know. Thanks for the help.

[Dalex]

I know this sounds simple but did you try a new spark plug?

Even if you clean a fouled plug some times they just dont have enough spark.

[Spikers400]

Iv tried 3 different plugs. All brand new. Im goign to go out and try sum starter fluid.

[kilabeez0]

Nobody has answered your question. Yes there are two TDC's. You want to be on the compression stroke. This tells you how to check. It may be 20 years old, but it's the same damn air cooled technology.
http://www.3wheeler.org/dirtwheels/6-87~tuneupindex.html

[MIKE400EX]

You can set the cam up on "either" TDC, they are one and the same.

[MIKE400EX]

Spiker, I don't think anybody meant to imply that you put the tensioner on before the chain - that would be very hard to do. LOL
What was meant, was to put everything together except the tensioner. Then with it all lined up, put the tensioner on and then double check that the timing is still correct. Just to be sure, turn it over twice (by hand only), CCW when looking at left side of the motor, and check the timing again. If it's still OK then look for something else like valve clearances etc... Since you also mentioned that the plug keeps getting wet, check the carb out.
Just curious, did it run OK before the cam change? What else was done to it when the cam was changed? What cam is in there now?

[Spikers400]

Thanks guys for the help. Well he bored the cylinder, put a 416 piston in, and its a stage 2 cam. It ran fine before the mods. I just got a compression tester so i am going to check the compression tommorow. Hcr400ex also did a valve clean up, lapping etc. So i am thinking he put it together wrong or sumthign maby they are leaking.

[BLEEDRED]

It took a little time to get it started, and when it started it did not want to idle(possibly due to the replacement of his idle screw). But if he kept it above idle it ran good, and strong.


This is what confuses me the most. I just read this whole thread and for some reason this portion of the orginal post seems to have been missed. Everybody jumped to whether or not the cam is 180 out or not...

I'm at a loss here, but could somebody please explain why if the timing is a little off or the cam is 180 out the quad "ran good, and strong" after it was assembled and now it doesn't run at all.

[Spikers400]

What i meant was, he just replaced the idle screw in his carb, because it was broken. So i figured the poor idle might have been due to a misproperly installed idle screw.