Need help after top end install

[JRN2786]

Got everything back together, had the timing a tooth of i think the first try, correctected the timing. Now it seems to run good but it white smoking BAD and it wont idle. I rejetted the carb correctly. With the idle screw all the way out/in whatever it still wont idle. So is it still out of time? Thank you for any help

[JRN2786]

Don't know if this matters but I didn't adjust my valves when I did all this cause they were adjusted right before I took it apart.

[AtvKid4Eva]

Does the smoke smell like burning oil?

[JRN2786]

Nope almost smells like race gas. But it has 93 in it kinda weird. Woo the timing being off a toothed make it smoke? Doesn't seem like it would to me

[jcs003]

did you put your piston rings on correctly?

[JRN2786]

They were already on the piston. Came out of a good running quad with about 4 hours on it

[jcs003]

was your bore matched to the piston?

[JRN2786]

QUOTE]Originally posted by jcs003
was your bore matched to the piston? [/QUOTE]
Yep

[CJM]

I know ive seen this same issue once before and there was a fix, but memory escapes me.

I want to say it had something to either do with the carb, head gasket or the timing chain-but Im not sure. Steve or Ron, you remember anything like this?

I would start by verifying you have good compression. Stock good range is 100-128psi. Bad compression means its leaking from somewhere then, either rings or headgasket.

[JRN2786]

I don't have a compression tester. But I replaced all gaskets with new ones and torqued everything by specs. I hope its just outa time. I don't see what else it could be. It did not smoke at all before I took it apart but it never did wanna idle before or. After the rebuild so I don't know what the hell is wrong

[JRN2786]

BTW. I used assembly lube when I put it together. Could that cause the smoke? I've only ran it about 5mins but something seems wrong with it not being able to run at lower RPMs

[tri5ron]

Am I understanding this correctly ?

Was this a used piston and used rings (with 4 hours on them), ...
that had already been run in one engine,...

and now it has been installed into another engine with the same rings ???

[CJM]

When i do a topend, I use 2cyl oil to lube the cylinder up a bit and put the piston in. It will smoke of course but then go away.

It might be outta time, only way to tell is to put it at TDC, check the lobes are faced down on the cam and the cam marks line up with the head.

[JRN2786]

Yes but I'm using his piston and cylinder. It ran great in the other quad

[JRN2786]

Is there anyway the cam hub could have been put ok the cam wrong?

[CJM]

The cam gear you mean? Sure it coulda been.

When you assemble that topend you gotta have the lobes the cam down and then you must line up the marks of the cam gear, there are 3 marks. 1 points up and the other two line up parallel with the head.

Another thing is your cam chain and tensioner could be a bit worn out. When everythings tight you shouldnt be able to move that chain much at all.

[89trx250r]

it really sounds like your valves arent in spec think about it youve got smoke from the exhaust which generally indicates something having to do with valves and then to top it off it wont stay running well obviously if your intake or exhaust valves are sticking closed or open its not gonna run correctly or idle properly

[JRN2786]

Originally posted by CJM
The cam gear you mean? Sure it coulda been.

When you assemble that topend you gotta have the lobes the cam down and then you must line up the marks of the cam gear, there are 3 marks. 1 points up and the other two line up parallel with the head.

Another thing is your cam chain and tensioner could be a bit worn out. When everythings tight you shouldnt be able to move that chain much at all.

It has a new tentioner and I'm talking about the cam being put into the hub on the wrong spines not the socket. Thanks for the advice though

[CJM]

Originally posted by JRN2786
It has a new tentioner and I'm talking about the cam being put into the hub on the wrong spines not the socket. Thanks for the advice though

Im not exactly sure I follow. Your talking about the hub piece itself that goes on the cam thats off maybe a few degrees? I was not aware they came off but it is possible I guess.

It would matter as then the cam lobes would be off slightly even if the cam gears in place.

I would take it apart and assure everything s good.

You did replace the cam chain as well right? Good tensioner but bad chain will cause it to jump as well.

Id start top to bottom verifying things like rings, cam timing, valves, etc are all correct.

[JRN2786]

Yeah the hub that slides on the cam is what I am talking about. No new cam chain but mine is tight as can be. I don't see how the valves could be off adjustment when it hasn't been run. Not saying they aren't but how they be wrong after not running it?

[CJM]

Its possible the valves were off before you began. I always check them to be sure if Im in there.

It is possible the splines on the cam gear hub could be off. About all I can suggest is to make sure its straight up and down like the lobes. Might be a marking on it as well, not sure since I have a hotcam.

[WoodTRD]

When I put mine back together after swapping the head and cam it fired right up and ran fine but smoked pretty good for a little while then quit. If I remember right it was first white smoke then a little bluish but by the time I was done breaking in the cam it quit and has so far been good since. Think it took around 15-20 minutes to quit but I'm not sure.

Not sure if this helps or not, but when your timing mark is lined up on the compression stroke the lines on the cam sprocket should line up with the head, lobes should be down, and the cam sprocket bolts should be vertical or pretty much so. Theres a wide spot of teeth on the stock cam that lines up with a spot on the sprocket, and hotcams have a dot on the end to line the gear up with (at least on the old style you have to press the stock sprocket on)

[JRN2786]

Mine is a hotcam also where is the mark at cause I don't see one on mine it may be an older one

[WoodTRD]

Mine's one of the old style hotcams you have to press the sprocket flange off of the stock cam and onto the hotcam. On it there's a dot on the end of the splined end of the cam to line the flange up with when you press it on

[JRN2786]

OK, I rode it up and down the road today for about 15 minutes and it quit smoking most of the way just a little white smoke now and then, It runs great so its not out of time. I thing it was just burning off all the assembly lube. But anyhow I am very happy i dont have retime it and its running good just needs broke in. I think the 172 main jet is too big there is alot of sparks comeing out the exhaust when i let off the throttle it seemed like it sparked less the more i rode it. thanks for the help everyone

[CJM]

What is the motor, stock modified, open airbox, cam etc?

170ish or so main is for larger bore, Id try a few sizes lower.

This chart will help: http://www.exriders.com/vbb/showthread.php?s=&threadid=445695&highlight=jetting+placement

[JRN2786]

Mods are in my signature now yeah I seem the chart I'm probably gonna put the 170 main in after I ride it a few hours and the do a plug chop and go from there

[CJM]

Im running a very similar setup and Im near sea level and while Im a tad rich with a 172 I think Im ok.

[JRN2786]

Yeah im around 600ft above sea level. so were pretty close on the jetting I think.