87Iroc

I have jug off now. Will take a look at rod and look for bends. I don’t know history of it before my friend. At some point it may have but don’t think it was when friend had it. He said it was a gradual popping on decels and then it quit on him. Said he was going 3 mph down driveway when it quit. no visible bends. Shows heat but assume that’s from assy as whole thing looks pristine inside

I have jug off now. Will take a look at rod and look for bends. I don’t know history of it before my friend. At some point it may have but don’t think it was when friend had it. He said it was a gradual popping on decels and then it quit on him. Said he was going 3 mph down driveway when it quit.

Decided I didn't need anotehr pic that shows the same thing. I have gone through everything inside the engine and it all looks up to par. Timing is dead on in rear(using mark on the back that Shadetree told me about makes life much easier to visualize) and you see what it says above. About 1/2 tooth off if that). I pulled the cam last night to ensure the cam decompressor 'thing'. It moved side to side. Locked in the correct direction. Unlocked in the other with a bit of a click. So now I am going to reassemble the engine and put it back in. Then start trouble shooting other items. Should have started here but I was sure the timing was still off. Oh well, it was fun getting to 'know' the engine. So next up... Reinstall Engine Recheck the engine, ensure we didn't inadvertently fix anthing(we did relap valves as exh didn't look right, brother fixed a loose spade connector(which was on a new part anyway) on the pickup by flywheel, and I think that's all we 'fixed' while it was apart). Start through fault tree in Honda manual. It did backfire through carb...but only after about 5 starts(Start, run a second or 2, die, restart, etc). And it was a very minor backfire. Figure to hook up the bare minimum in case I have to pull it again.

Brothers and I lined everything up this today. Their opinion is timing chain might be off a half tooth but not a full tooth. I plan to get a more definitive pic to post Monday likely. Neither valve is bent. Exhaust valve seat didn’t look right so brother lapped valves in so they looked a lot cleaner. (Previous owner said 90 psi compression when he checked) Exhaust seat had some rust colored pin head size dots all around it. Just looked scuzzy. After lapping it looks a lot better. Even shiny surface all around. We pressurized cylinder and it held 150 psi of shop Air. pulled off rear cover and inspected flywheel visually. It was round with magnets and I could see key in key way. 🙂 stator was replaced while apart and the pickup for flywheel varied voltage like it should. Unsure where to head next. One thought they had is exhaust valve ‘lift’ for starting isn’t working and bleeding pressure After it tries to start. I did not bring that part with me for them to see.

I just super checked cam and t. They actually don’t quite line up right. Pic shows whe T is in middle of timing hole perfectly. Appears off a bit

I am scratching my head right now. Pulled recoil off back. That line points down at TDC. When I line the starter line up with triangle cam is 90 degree out from where it should be and no T in viewing hole. When I get t lined up the cam looks right. should all 3 line up happily in unison? Is that starter ‘dog’ keyed or could it be assembled 180 out and still have engine happy?

Yep....so here's the thing. I can line the timing mark up, due to cam going 1/2 speed of crank, at both 'correct' and 'incorrect'. The front of cam, when T is lined up, looks like the pic in the Clymer Manual(notch in nose of cam at bottom, timing dot on came sprocket pointed at mark on case). I can then spin crank 360. LIne mark back up, and have the front of cam look backwards. I am a Small Block guy with a distributor and I know you can set those 180 out...but my assumption here is it is right as there is no distributor to worry about it is correct. I sat and thought about it a long time out there but I think its right(that is probably where my hesitation came in above). If I need to think of this a different way, let me know. I noted there is a T and a F on the flywheel. Took me a while to sort it all out!

I have Honda manual too...but the Clymer manual goes to garage easier than my laptop. I'll study the Honda manual too on this stuff. Thanks for heads up there may be deficiencies in Clymer manual

I have it out and on bench. Pulled head and front cover. I think timing is set right. I can get The flywheel T to line up at right time. So that setup looks right. The exhaust valve area looks super toasty to me. Intake seat is shiny all around circumference but exhaust is not. All around seat has some pits in it. Valve spring seat area is bluish and toasty looking. Chucked them up and can’t visually see they are out of round but more study is needed. Gonna check on kitchen counter. We are going to lap valves in at brothers this weekend. See how that goes. If anyone finds a valve keeper flying thru the air. Send it my way. 🙂 piston to top of jug clearance is .009 with my feeler gauges and drywall knife flat edge. Piston appears dished a bit so that’s out at very edge. Friend said compression was 90 psi when he checked it. I did not have a tester so I did not recheck. 15 yr old daughter helped me swing engine out and lift to bench. Was kinda proud. 🙂

Bent Valve....hmmmmmm. OK. A compression check would show that, right? I can also pull the head and drop valves and take a look. I think the old owner already did that, but can check for bent as he may have only been looking for burnt. He said he saw no signs of piston to valve impact. Would you be able to pull the 'jug' and piston and look at the rod to see if its bent do you think? Just trying to avoid splitting the cases. My friend said it started popping last year and gradually got worse to point of not running. I would think a bent rod would be an instantanous 'failed' situation. Thanks for the input!

Thanks Everyone!!

Good evening. Looking for some help... I bought a basket case 98 450S Foreman from a friend last night who was at his last legs trying to figure out what the dealer diagnosed as a timing chain slip. He was afraid the engine needs the bottom end rebuilt and he had spent too much money on it already...so I made him an offer and he took it. Symptoms are it will start and run, but won't respond to throttle, won't idle very long(seconds) until it dies. I tried starting it several times when I got home with it and noticed a blue flame emanating through the carb as it dies. You can hear the starter(I think) do a 'sproing' sound as it dies too. It's very hard to pull start too. I'm a big guy...and it is tough. So the dealer diagnosed a timing chain failure. My friend refused to pay their '1500 to start' quote and did it himself. He's a tinkerer and has rebuilt car engines in the past successfully. Very meticulous. So he tore into it. Put new timing chain, tensioner, inspected piston, bushings, etc. He replaced everything he could as he had it apart.he doesn’t believe it jumped time. He does/did product validation at an engine company...so is familiar with inspecting torn down engine parts. He also put a new CDI box, new main harness(found a short in the old one), new carb. He was planning on keeping it so they are all Honda parts. The timing chain was another 'odd' brand but said it was a subsidiary of Borg-Warner or something. Said it wasn't a cheap china chain he did all of that work...put it back together after finding no smoking gun and it’s exactly as it was before he tore into it. I swapped the 2 cdi boxes he had last night back and forth with no change. He was afraid the bearings were binding in the bottom end and the engine needed a bottom end rebuilt. At that point, he was done. He had replaced everything he thought could impact the timing and it still acts the same as before the work. I think that it if was bearings in the bottom end, it would respond to throttle, it would at least act like it wanted to run...and would get worse as it heats up. So reading the Clymer manual, there is a little blurb(keep in mind, I know little about motorcycles or ATVs)...it said 'if it is backfiring, your timing is off and is non-adjustable, check <several things> as well as the key on the flyhweel to ensure it is intact'. <--something to that effect. My friend never pulled the engine, he did all work in chassis and I trust he did it right(unless there is some trickiness to it, but my presumption is he did it to the best of his ability right)...so I am thinking he may have a sheered flywheel key and not caught it although he now says he pulled flywheel in chassis I didn’t know that was possible but I know he replaced The stator back there. my current plan is to pull engine(3 bolts away from it coming out right now) and without standing on my head like he did check his work. Inspect flywheel. Timing setup. Etc. a couple questions... 1) I want to get a gasket set on order. Thinking full engine set as I have no idea what I'm going to get my hands in to....any manufacturers/warnings of places to avoid? 2) any credence to his bottom end worries? Any way to check while engine is on bench to health if bottom end? Thanks! Greg

Quick intro. First time atv owner. Child of the 80s so first one I ever attempted to drive was a 200S ATC. Haven’t owned one before but landed a 98 Foreman 450S basket case. Most of my adult life has been spent tinkering with cars and raising a family. Look forward to learning about my new purchase here. greg