99 400 ex woes

[atvdad68]

my son has a 99 400 ex that he bought and ran fine for a while. the other day he was riding and it quit on him and couldnt get it to turn over again. all it did was just click at the seleniod by the battery. i think something locked up inside the motor. when he tried to push start it i think it un locked it and now it will start but has a rattling sound coming from inside the engine. he says it has just as much power as before but the sound coming from the engine has me worried that something is broke in it. anyone care to take a guess as to what it might be that can cause this. im a 2 stroke guy as far as working on motors and i never been inside a 4 stroke...thanks in advance,Brian

ps im downloading a service manual as i write this

[Gibson]

it sounds like the starter is bad. is the noise coming from the left side of the motor?

[atvdad68]

sounds about the same on either side of the engine....its starts pushing the button now . but when this happened i think something locked up inside the motor when he was riding it( it just died) and when he tried to push start it it broke free. before he pushed started it all it would do is click when trying to start it with the button. after he pushed started it, it will now start with the push button,but makes a ratting sound like something is broke or loose inside the engine...the fact that it just clicked before and now will start with the push button makes me believe something broke and locked it up causing it to die when it happened and after he pushed it to start freed it back up so it will start with the push button but rattles inside when running

[extremetrucker]

Sounds like what mine did in a race once, just died, didn't lock when it did, but when you hit the button it was siezed, loaded up, went home, after it cooled off, I hit the button, fired up, ran good but with a grinding, rattling, stump grinder type sound, tore it down, bottom rod bearing was smoked, or another time it didn't die and wasn't siezed, the cam chain tensioner was bad, that made quite a noise too, but no lockup, if your downloading a service manual, and pay attention to what your doing, these things are really easy to work on, pull the top end off and check rod for play, I wouldn't run it until this is ruled out or you might be shopping for cases good luck with it

[atvdad68]

thanx for the info!...yeah it sounds just like you said,a mix between grinding and rattling

[extremetrucker]

No gaurantees, but that's what mine did, I don't think its a very common problem, and the top end is easy enough to tear off and check, hey on the bright side if that's what it is, good time to throw a stroker in there haha

[tri5ron]

My bets are your heading down the right path.
Keep us updated on what you find.
and BTW-
Welcome to the forums.
alot of good folks and good info. to be had here, ...
(and as with any forum,... a few loose cannons too).

[atvdad68]

thanks for the welcome....im going to man up and tear into it in the next couple days after i read the service manual a couple times...i'll let you know what i find

[atvdad68]

ok torn the top end off yesterday and found that there is play in the rod and crank. there is enough that when you move it up and down you can here it hitting each other...i think this is the problem, but not sure. i would think, that it should not have that much play up and down. am i right about this? we are thinking about putting a standard hot rod crank back in it and wisco piston and rings. sound like a good plan or do you recommend something better? thanks for all comments so far!!!, Brian

[tri5ron]

yes you are correct, there should be no play in the piston rod and crankshaft.
make sure you take a good look at the crankshaft to be sure there is no damage to it, you dont want to have to do this job a second time.

there are many options on pistons, bores, and compession ratio's.

If you are not going to race this bike,
and you are looking to maintain maximum reliability,
and you want to be able to still run pump gas,
my suggestion would be to stay as small on the bore as possible, (416 max.), and dont go over a 10:1 compression ratio.

I'm sure others will chime in on this, and I'm sure you'll get the full range of "you should do this..., you should do that", but I get the feeling that you are not looking to build it into a "maxed out maintaince menace".

This would also be a good time for you to consider putting in a upgraded timing chain and tensioner.
if the rod had enough time on it to go bad, then the chain and tensioner are probably getting pretty tired too.

might want to think about a full head/valve job too.

[powertechn2]

if you need, i think i still have my stock crank assembly, it had about 30 hours or so, was nothing wrong, i just built it up.

i have most of the old parts sitting around, cam, piston (like i say, really low hours) and i think i do have the crank, i dunno, ill have to look to be honest... its been a lil while lol.


but as others have said, if you dont plan on racing it, and didnt think it needs more power, dont build it larger than you have to go to just get it up and running good again.

[atvdad68]

no we arent going to mod it up any. thats why i was thinking of going with the standard hot rod crankshaft and standard bore wiseco piston and rings kit

[atvdad68]

powertechn2 please look and see if you have it ...thanks

[powertechn2]

i have the weekend off, and being as my quad didnt arrive this week as i was promised (salesman... no further explanation necessary) ill look tomorrow as i will be cleaning the shed out of boredom.


if ya dont hear back from me tomorrow (saturday) , reply again

[atvdad68]

any links to the tool i need to get the fly wheel off..or any home tricks that work quite well? hang on im going in!!

[monkeyballs]

Originally posted by extremetrucker
Sounds like what mine did in a race once, just died, didn't lock when it did, but when you hit the button it was siezed, loaded up, went home, after it cooled off, I hit the button, fired up, ran good but with a grinding, rattling, stump grinder type sound, tore it down, bottom rod bearing was smoked, or another time it didn't die and wasn't siezed, the cam chain tensioner was bad, that made quite a noise too, but no lockup, if your downloading a service manual, and pay attention to what your doing, these things are really easy to work on, pull the top end off and check rod for play, I wouldn't run it until this is ruled out or you might be shopping for cases good luck with it
You mean, the bottom connecting rod bearing?

[powertechn2]

Originally posted by atvdad68
powertechn2 please look and see if you have it ...thanks



Well, i looked high and low, cant find the crank anywhere.

i dunno what i would have done with it.

i have used but not used up piston, a good cam (stock) some valves, i think intakes, valve springs, extra clutch plates and springs, a NEW white brothers air filter (foam, still in package) a header pipe, a carb jetted for stock engine with w-b full system and K&N filter, stock cdi... but cant find the damned crank. go figure.


Sorry.

[atvdad68]

do i really need all of those fancy tools to replace the crankshaft and bearings that the service manual says ? ive looked and cant find any links where to buy them

[monkeyballs]

B4 you put the crank in get some one witha dial indicator and v blocks and put the crank on it and check if there is perfect..