first time in a four stroke...need help

[tecatecrazy]

well I suck at four strokes and am not sure what to do next so I thought I would consult before damaging something. so.. for some reason I decided the 70 needed a cam (needs other things worse) so I bought one from ebay that said that it would be easy to install and.... it was. but now when I start it ,it wont idle and the power took a huge poop. did I mention that terrible hammering noise coming from the head. I made sure to mark the cam chain with the cam gear so that I put it back together right. the only thing I can think is that I got off a tooth. was this cam a stupid idea or what? also is it necessary to rejet for a modified cam? anyway here is what I bought. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=170024761072&ih=007&sspagename=STRK%3AMEWN%3AIT

[tecatecrazy]

an added note. with the "T" on the flywhell lined up with the mark on the case the "O" on the cam gear is half a link before the the mark on the head. so if I advance it cam one tooth the "O" mark will be half a link past the casting mark on the head. if that makes any sense

[TravEX]

Make sure the cam lobes are down when you have the motor at TDC. I hope you didn't damage the valves. How long did you run it?

Travis

[tecatecrazy]

5 minutes or so. it still starts and turns over like it did before

[TravEX]

I left out part of a sentence. Make sure the cam lobes are down when you line the cam sprocket up to put the chain back on, with the motor at TDC.

Travis

[NewOldSchool]

well...i ran into a similar problem on my 185......i had two part trikes......i had a 185s motor with a bad cylinder and a 200 motor with a bad tranny.....i switched the top ends and i dont remember which cam it was.....but i had to get the timing just right or else the valves would hit the piston.......how did i solve that problem? i wanted advanced timing so i jsut notched the piston out where the valvle was hitting.....ghetto i know........but it served its purpose......what im getting at is......you might have gotten the wrong cam maybe for a bigger motor but it fit......you can notch out the piston or get the timing just right......that hammering noise could be your timing chain too

[tecatecrazy]

well I think the ghetto notchin' is out :lol: . I decided to go have another try. It started right up with no knockin' this time (guessing that was a lubrication issue) and it will idle with the idle screw turned in another 1 1/2 turns in but it still lacks power. seems like it might be a jetting issue. of course this motor has probably never been rebuilt. would an aggressive cam have a negative impact on a tired engine or do I just need to bump up the main a couple of sizes. sorry for the inexperience. everything should be a two stroke.

[TravEX]

I wouldn't mess with different cams on the 70, most of the times you're looking at different lifter or rockers with the different cams. A fresh rebuild will liven it up.

[NewOldSchool]

i agree with you on the two stroke issue.....but my "notched out" motor still runs to this day....your power issue might be due to low compression....but you being a two stroke man im thinkin that was one of the first things you looked for......idk man........ rebuild? you decide....ive already given my two cents