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87Iroc

Timing problem or ???

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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

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A bent valve or connecting rod will also make it run like it is out of time ----- if your no throttle responce is mid range to full throttle , check the diaphragm of the slider in the carb , if it has a crack , hole or not sealing it will do just that ----

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Posted (edited)
3 hours ago, Fishfiles said:

A bent valve or connecting rod will also make it run like it is out of time ----- if your no throttle responce is mid range to full throttle , check the diaphragm of the slider in the carb , if it has a crack , hole or not sealing it will do just that ----

 

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!

Edited by 87Iroc

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with the head off the piston should come flush with the top of the jug , if not the rod is bent , water will cause the rod to bend as water don't compress

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versha engine gasket kits, or namura complete engine gasket kits, complete engine oil seal kit should get you started. my first plan of attack would be : see if the timing is indeed correct ?. pull the head off, remove the valves, run them in a drill, watch to see if they wobble ?. if they do ?, they are bent. as for cam chains ?, i run nothing but D.I.D. brand. deff give the carb an over haul, shindy carb rebuild kits is all i use in my carb over hauls. you will need a clutch puller tool if you plan on splitting the cases ?. if your not gonna split the cases ?, no need in buying a complete engine gasket kit. if you do find out your rod is bad ?, then yes, you will need a complete engine gasket kit. BE SURE TO CHECK YOUR ROD FOR PLAY AT BOTH THE TOP AND BOTTOM !!!. exhausting out the carb tells me the timing is off ?, or a bent/bad valve ?. keep us informed , lots of us know this model inside and out !..lol.

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Posted (edited)

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. 🙂

 

 

 

EB37A2D5-B6A8-4F99-A58E-66F7B1438CEC.jpeg

C8722EAC-20C0-4E43-AD0C-E1A98AAEA058.jpeg

Edited by 87Iroc

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18 hours ago, 87Iroc said:

So reading the Clymer manual,

 

you don't need to depend on that ^^^^^ you need a honda shop manual....  for your perticular machine. 

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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

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22 minutes ago, 87Iroc said:

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. 🙂

 

 

 

EB37A2D5-B6A8-4F99-A58E-66F7B1438CEC.jpeg

C8722EAC-20C0-4E43-AD0C-E1A98AAEA058.jpeg

very important !!!. you say you believe the timing is correct when you looked at the marks and index ?, my question to you is, was the timing marks checked when the piston was on top dead center on the COMPRESSION STROKE ?, AND NOT THE EXHAUST STROKE ?.

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my last post ^^^, if the timing marks show to be on the exhaust stroke, and not the compression stroke ?, well..there is one of your problems right there !.

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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! 

 

 

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4 minutes ago, 87Iroc said:

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! 

 

 

here's how i do it, and you can check it if ya want ?. first, i pull the spark plug, then i pull the pull starter off the back, under it, is the pull rope cage, on one of those '' tangs '' is a line, this line runs from the front of the tang, to the back towards the engine case. if you look right above and behind that line, there is a triangle , it points down, this triangle lines up with the line on the tang. back at the front, behind the clutch cover, up in left hand corner, is your cam, above the sprocket is another triangle, this is your index, on the cam sprocket is a punch mark, this punch mark lines up with the index at the very top. if none of this lines up right ?, it makes me wonder if the PO turned the cam sprocket 180 out , and bolted it back on the cam ?. make sense ?.

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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?

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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

BF043403-C942-418D-AC12-B85DF7FC738D.jpeg

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3 minutes ago, 87Iroc said:

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?

all timing marks should line up !.

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1 minute ago, 87Iroc said:

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

BF043403-C942-418D-AC12-B85DF7FC738D.jpeg

cam mark looks good, what does the T mark in sight hole look like ?, and what about the timing marks at the back of the engine look like ?, all 3 should be dead on, with the piston at top of cylinder.

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8 minutes ago, 87Iroc said:

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?

tells me, your cam is not timed right..lol.

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Posted (edited)
On 5/21/2020 at 8:13 PM, shadetree said:

all timing marks should line up !.


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. 
 

 

 


 

 

Edited by 87Iroc

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Posted (edited)

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. 

Edited by 87Iroc
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Quote piston to top of jug clearance is .009 with my feeler gauges and drywall knife flat edge.  

 

Wonder if this engine was ever gagged with water 

 

Did you slide the jug off and visually see the connecting rod , just a minimal bent will make it run like crap ....009 and a draw wall razor edge don't ring a bell 

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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. 

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Posted (edited)

7CB1A449-42C3-4FB6-9746-D4D676D7612A.jpegI 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

 

7CB1A449-42C3-4FB6-9746-D4D676D7612A.jpeg

Edited by 87Iroc

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43 minutes ago, 87Iroc said:

7CB1A449-42C3-4FB6-9746-D4D676D7612A.jpegI 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

 

7CB1A449-42C3-4FB6-9746-D4D676D7612A.jpeg

looking at the side of the piston in this pic ^^, i am concerned about that one side at the top being '' burnt '' ??, why would one side be that way, and not all the way around the top edge ?, reason: rings ?, cylinder out of round ?, rod slop at wrist pin ?. now is the time to check the cylinder with the rings, and see what clearance you have on end gap ?.

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Fair.  I hadn’t noticed that. I wiped it all off with my finger after i read the post. Checking rings now. 2nd ring was bound in groove a bit. 

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