pdrhodes57 0 Posted July 3, 2022 So I’ve got a 680 I just rebuilt the top end in. All new components and also the only reason for the build was a light smoke caused by the rings being worn. I can’t get it to start, I’m positive it’s timed correctly. The only was it will run for any time at all is if I choke the intake with my hand. Thanks for any help I’m stumped on this one Share this post Link to post Share on other sites
shadetree 5,977 Posted July 3, 2022 welcome, my money say's you got the timing off ?, or your throttle body is not working right ?. if it was running before you did the top end ?, then chances are, you got the timing off 180. check to make sure you got the timing set on the valves for compression stroke ?, you prob set them on exhaust stroke ?, it must be set on compression stroke. 2 Share this post Link to post Share on other sites
pdrhodes57 0 Posted July 3, 2022 Thanks glad to be here! So how do you decide if it’s on the compression stroke if the head is off to check the timing? I feel like the service manual didn’t mention any of this lol Share this post Link to post Share on other sites
shadetree 5,977 Posted July 3, 2022 4 hours ago, pdrhodes57 said: Thanks glad to be here! So how do you decide if it’s on the compression stroke if the head is off to check the timing? I feel like the service manual didn’t mention any of this lol '' So how do you decide if it’s on the compression stroke if the head is off to check the timing '' this has been said sooooooo many times on the forums here, but i'll try to lay it out once more..i need to make a sticky on this ?..as i'm getting kinda worn out by explaining to members on how to set and adjust timing on atv ( honda's ) engines..lol. by watching the intake valve ( valves ) ?, you can tell which stroke you have the piston set when doing timing. with the piston on TDC ( top dead center ), you rocker box off, rotate the pull starter ( if you have on ? ) with a 17mm ratchet and socket counter clockwise, as you are doing this..watch the intake valve, if it starts to go down when turning the crank backwards ?, then slowly turn the crank back to line up the tab on the pull starter ( the tang has a line on it ) it lines up with the raised arrow behind the pull starter stamped in the case cover, line these up. check the site hole for the letter T, make sure these are lined up, piston should be on TDC. if for some reason when you first started turning the crank backwards, and the intake valve did not start to go down ?, then slowly turn the crank to where you first started, then keep turning it all the way around until the timing marks line back up on the pull starter, then from here..rotate the crank backwards slowly...the intake valve SHOULD ?..start to go down, if it does, turn it clockwise back to the timing marks on the pull starter and stator case, adjust the valves, lock them down, DONE !. Share this post Link to post Share on other sites
pdrhodes57 0 Posted July 3, 2022 (edited) Okay sorry I misunderstood I guess. My bad. I’ve already done what you just mentioned with the valves, taking your advice from another thread somewhere. I was talking about timing the camshaft. The way I did It when I rebuilt it was set the cam with the 3 timing marks (one down and 2 parallel with the cylinder) So just to be clear, when I’m setting the timing on the camshaft as long as it’s tdc that’s fine right? Edited July 3, 2022 by pdrhodes57 Share this post Link to post Share on other sites
LedFTed 1,143 Posted July 4, 2022 Not to say, this is a problem,. if ya do the top, ya gotta do the bottom.. or vice-versa. maybe it dont apply to ATV's... Share this post Link to post Share on other sites
toodeep 1,760 Posted July 6, 2022 On 7/3/2022 at 11:50 AM, pdrhodes57 said: Okay sorry I misunderstood I guess. My bad. I’ve already done what you just mentioned with the valves, taking your advice from another thread somewhere. I was talking about timing the camshaft. The way I did It when I rebuilt it was set the cam with the 3 timing marks (one down and 2 parallel with the cylinder) So just to be clear, when I’m setting the timing on the camshaft as long as it’s tdc that’s fine right? The bottom mark on the cam sprocket. Did you lay anything flat along the head surface to check that? If the motor was still in the machine it can be hard to get a good view on that mark. It's easy to get them a tooth off especially if the chain is stretched some. Share this post Link to post Share on other sites
pdrhodes57 0 Posted July 7, 2022 (edited) I have to get around to checking the timing, in other news I got it to run by choking it and then it ran great honestly. Revved out, idled fine, no backfires, but I’d kill it and it wouldn’t start again unless I choked the intake again. Would it do that if it was a tooth out? It definitely has me stumped at this point, it’s just being weird lol Edited July 7, 2022 by pdrhodes57 Share this post Link to post Share on other sites
jeepwm69 7,751 Posted July 7, 2022 Stupid question, but are you running it with the airbox lid off? 1 Share this post Link to post Share on other sites
pdrhodes57 0 Posted July 7, 2022 Yes but I’ve let it run and put it back on and it didn’t change anything. Share this post Link to post Share on other sites
pdrhodes57 0 Posted July 18, 2022 On 7/6/2022 at 11:40 PM, pdrhodes57 said: I have to get around to checking the timing, in other news I got it to run by choking it and then it ran great honestly. Revved out, idled fine, no backfires, but I’d kill it and it wouldn’t start again unless I choked the intake again. Would it do that if it was a tooth out? It definitely has me stumped at this point, it’s just being weird lol Still having the same thing going on, I can choke it with my hand until it cranks, then it literally runs perfect without any issues until I kill it again, then same scenario. Also choking it makes it turn over easier Share this post Link to post Share on other sites
Fishfiles 20,147 Posted July 18, 2022 Bent connecting rod ----- water ingestion , ever took a dunk ? ---- Share this post Link to post Share on other sites
pdrhodes57 0 Posted July 18, 2022 No never been under Share this post Link to post Share on other sites
Fishfiles 20,147 Posted July 18, 2022 46 minutes ago, pdrhodes57 said: No never been under There are other ways to bend a rod , since your 680 is throttle body , I am not sure if it can over flow into the cylinder like a carb can and hydrolock with gas , but , being out of time , or the piston hitting a valve by a stuck valve can cause a rod to bend --- the reason I say that is I had a 300 bend a rod , and it would take hard choking to get it started , like you mentioned ,by putting y hand over the snorkel pipe ---------- I remember the lid of the air box would pulsate up and down with the bend rod Share this post Link to post Share on other sites
pdrhodes57 0 Posted July 18, 2022 On 7/6/2022 at 11:40 PM, pdrhodes57 said: Well that’s concerning lol. I’m hoping that’s not it. I’m going to recheck the valves and see if maybe they’re too tight Share this post Link to post Share on other sites
jeepwm69 7,751 Posted July 18, 2022 I know when I rebuilt my buddies rincon the rod/ crank was fine on it. I don’t remember exactly what caused the issue that pdrhodes is having, but he found my old thread on the old board where I was asking about it. @pdrhodes57 have you replaced the battery? Share this post Link to post Share on other sites
pdrhodes57 0 Posted July 19, 2022 On 7/6/2022 at 11:40 PM, pdrhodes57 said: No never replaced battery but im using a new car battery to jump it off Share this post Link to post Share on other sites
pdrhodes57 0 Posted July 19, 2022 Well not jump it off but I’m using jumper cables to hook it to the existing leads Share this post Link to post Share on other sites
jeepwm69 7,751 Posted July 19, 2022 I’d try actually connecting it to a known good battery Share this post Link to post Share on other sites
pdrhodes57 0 Posted July 19, 2022 Yeah I need to buy one for it, I just didn’t think it would matter considering it’s needs like 270cca and this battery has like 600cca Share this post Link to post Share on other sites
jeepwm69 7,751 Posted July 19, 2022 Yeah, but you need big heavy cables with a good clean connection if it’s not bolted to the cables Share this post Link to post Share on other sites
