Serious timing problems

[DerbyDerb47]

I took my honda which has a hot cam two and a 11:1 piston to the honda shop to see why my valves wear still hittin the piston when the timing marks lined up correctly. I got a call back last night say that my timing is off 180 degrees, but the timing marks are still lining up right. How is this possible??

[01boneless]

sounds like the cam is in wrong or something are the lobes down with the lines lined up?

[NacsMXer]

It's not possible for the timing to be 180 out on these motors due to the redundant spark...that's a fact.

You have other issues going on if the valves are contacting the piston.

[DerbyDerb47]

Ok thats what i thought. I adjusted the valves perfect, and i put made sure the lobes were facing down. So everything is in perfect timing, and yet they still hit the piston. I tore the clutch cover off and made sure the chain was in good shap and it is, an i also check to see if the crank bearings wear ok, and they look perfectly fine also. So im completly confused at this point..

[DerbyDerb47]

And i also made sure it was on the correct stroke as well and its still doin the same thing, slappin the piston with the valves.

[DnB_racing]

degree your crank and cam, to find your real TDC and valve lift and cam center, not the lines!! with the HC2 you should have 9mm intake lift
then when all lined up and timed right, do a squish test.

maybe your head has been decked or your gaskets are thinner then stock

I always check the squish, as some cylinders and heads have slight different tolerances

but with all the tolerances between the crank, piston,rod,cam and chain, and gaskets its not uncommon to find it out of time a half a tooth or more when performing a TDC check with a degree wheel

or are you sure you dont have a bent valve stem hanging it up?

[matts27]

Mic the lobes on the cam. Could have gotten a bad grind. Is it contacting on the compression or the exhaust stroke??? Also, try loosing the rockers up twice as much clearance .12 and see if they clear the piston. Might need a timing sprocket for the cam to degree it slightly off TDC to correct the issue. One other question, is the piston in backwards, meaning the larger reliefs are in the front and the smaller in the back?? That could do it, just trying to shoot some variables out there, Matt

[DerbyDerb47]

No this piston is in the bike correctly. The bike has about 10hrs or so on it with all the after market parts. It just decided one day to start makin this harsh slappin noise when i was ridin in the woods. I tore it apart and noticed my exaust valves had some rough edges on them so i replaced them. I already tore the valves back off to make sure they are in the head correctly, and everything seems to be correct. This bike did run real strong, just now its got problems out of no where.

[DerbyDerb47]

And its slappin on all four valves with them adjusted to spec and when i took them and ran them loose so they wouldnt have as much pressure on them thinkin maybe i just had them gapped to tight, but this is not the case.

[matts27]

Is the cam new, just dropped it in? Something had to change in the last 10 hrs. of riding the bike, either that or the valves were hitting all along. More info the better, Valves are controlled by the cam, the piston tolerance to head can't change unless you swap head gaskets. Either this problem was always there or you dropped in this cam, just trying to see what happened. TDC lines up on the crank with the cam and the rockers loose, no contact with the valves, coulda jumped a tooth I guess. Matt

[DerbyDerb47]

Nope its the same cam that I had at the begining of the rebuild. The only thing i can think of is the piston rod has just enough slopp to shove the piston up further then it should be

[DnB_racing]

Originally posted by DerbyDerb47
Nope its the same cam that I had at the begining of the rebuild. The only thing i can think of is the piston rod has just enough slopp to shove the piston up further then it should be are you sure it is a hotcam?
the reason I ask is some aftermarket cams require different springs.shorter valve guides and hardwelded rockers

and are much tougher on the head and valve train. maybe you got sent the wrong cam??? just guessing, but something to consider :confused:

[DerbyDerb47]

Yea im sure its a hot cam2, like i said it ran perfectly fine, until just one moment it decided to start making this noise. :confused: