Tick tick clunk! - Page 11

**jonathan180iq** · 08-30-2013, 10:01 AM

This photo shows the compression stroke. Both valves are closed and the blue air is being compressed. The very next thing that will happen is the spark plug will fire and it will all go BOOM! driving the piston down. Absolute bottom, the exhaust valve will open. As the piston is driven up, the gasses in the cylinder are expelled through the exhaust. On the next revoltution (after that TDC) the exhaust valve closes are the intake valve opens to draw in more air and fuel. Absolute bottom again, the intake valve closes and the piston, now driving up, compresses the air and fuel just before the big BOOM! (This final part is the TDC that we are concerned with.)

Goose51683 · 08-30-2013, 10:33 AM

Thank you guys. I know it seems simple and it is but with as much as I've been working lately, wrapping my head around this in the few hours I have after work is hard.

**jonathan180iq** · 08-30-2013, 05:59 PM

We know. It's not big deal.

Sometimes, having an extra set of eyes on a problem is beneficial... as if having a clearer head to look at something.
And sometimes having 6 pairs of eyes looking at something only confuses you. But I think we're all saying the same thing at this point. Now that you have at all together, you just have to figure out how much compression you're getting (almost none). So you have to figure out why you're not. You changed valves and seats, meaning your messed with the timing of everything, so this is a likely spot to have lost compression due to the system being open on an incorrect stroke.

The good think is that the system is self correcting after 1 part is right. So you only have to get them closed on compression and the others will be there. If there is no compression after that, then we just go from there.

**jonathan180iq** · 08-30-2013, 05:59 PM

Ps: In that photo notice the position of the lobes on the valves and the position of the valve heads themselves inside the chamber...

5th_bike · 08-31-2013, 05:35 PM

Here is a GIF:

[attachment=0:2f74kkyc]4StrokeEngine_Ortho_3D_Small.gif[/attachment:2f74kkyc]

You can easily see that at the end of the exhaust stroke, the valves out/in are still/almost being closed/opened (the cams are still/already touching the stems), but at the top of the compression stroke (where it sparks), both valves are closed and both cams are completely out of the way.

Water Warrior 2 · 08-31-2013, 11:40 PM

Can't remember if this was asked before but here goes. Are you sure the cam shaft is syncronized with the crank? If you got it one tooth out on reassembly the valve timing would be out. You might never get the compression you need. Said my piece so now the rest of the guys can run with it if need be.

JohnC · 09-01-2013, 12:36 AM

Quote:

Originally Posted by jonathan180iq

Ps: In that photo notice the position of the lobes on the valves and the position of the valve heads themselves inside the chamber...

The single cam on the 250 does not act directly on the valves. It pushes 2 rocker arms, one intake and one exhaust, up and each rocker arm pushes its 2 valves down.

+1 on Water Warrior's comment. One, ore maybe even 2 teeth out and it might still run, but not well. Any more than that and you risk hitting a valve with the piston and putting yourself back to square one...

Goose51683 · 09-02-2013, 01:22 PM

I've checked the TDC mark against the cam positioning more times than I can count. It appears my valves are closed when I hit that compression TDC mark as well.

I'm checking valve gaps again today but I though I would pull the top and check the timing again for shits and giggle.

Thanks for all the illustrations. Yet again the compression tester I got does not fit the bike so it looks like I have no choice but to order a specialty one to fit the 250.

Being the holiday I won't be spending to much time on this but I'll let all of you know if I do find anything

Goose51683 · 09-02-2013, 01:36 PM

Looking at the cam and lifters. Because the lifters ride on top of the cam I would want my lobes facing off or down at the TDC of the compression stroke right?

So would this be 180 off

alantf · 09-02-2013, 06:29 PM

Why not turn your photos to the correct position before posting them? makes things 100% easier for us.

08-30-2013, 10:01 AM	#101
jonathan180iq Super Moderator Join Date: Jan 2007 Location: Dalton, GA Posts: 3,996	Re: Tick tick clunk! This photo shows the compression stroke. Both valves are closed and the blue air is being compressed. The very next thing that will happen is the spark plug will fire and it will all go BOOM! driving the piston down. Absolute bottom, the exhaust valve will open. As the piston is driven up, the gasses in the cylinder are expelled through the exhaust. On the next revoltution (after that TDC) the exhaust valve closes are the intake valve opens to draw in more air and fuel. Absolute bottom again, the intake valve closes and the piston, now driving up, compresses the air and fuel just before the big BOOM! (This final part is the TDC that we are concerned with.) Login or Register to Remove Ads
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08-30-2013, 10:33 AM	#102
Goose51683 Senior Member Join Date: Apr 2013 Location: Indiana Posts: 621	Re: Tick tick clunk! Thank you guys. I know it seems simple and it is but with as much as I've been working lately, wrapping my head around this in the few hours I have after work is hard.
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08-30-2013, 05:59 PM	#103
jonathan180iq Super Moderator Join Date: Jan 2007 Location: Dalton, GA Posts: 3,996	Re: Tick tick clunk! We know. It's not big deal. Sometimes, having an extra set of eyes on a problem is beneficial... as if having a clearer head to look at something. And sometimes having 6 pairs of eyes looking at something only confuses you. But I think we're all saying the same thing at this point. Now that you have at all together, you just have to figure out how much compression you're getting (almost none). So you have to figure out why you're not. You changed valves and seats, meaning your messed with the timing of everything, so this is a likely spot to have lost compression due to the system being open on an incorrect stroke. The good think is that the system is self correcting after 1 part is right. So you only have to get them closed on compression and the others will be there. If there is no compression after that, then we just go from there. Login or Register to Remove Ads
	0

08-30-2013, 05:59 PM	#104
jonathan180iq Super Moderator Join Date: Jan 2007 Location: Dalton, GA Posts: 3,996	Re: Tick tick clunk! Ps: In that photo notice the position of the lobes on the valves and the position of the valve heads themselves inside the chamber...
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08-31-2013, 05:35 PM	#105
5th_bike Senior Member Join Date: Oct 2007 Location: HoCo, Maryland Posts: 1,349	Re: Tick tick clunk! Here is a GIF: [attachment=0:2f74kkyc]4StrokeEngine_Ortho_3D_Small.gif[/attachment:2f74kkyc] You can easily see that at the end of the exhaust stroke, the valves out/in are still/almost being closed/opened (the cams are still/already touching the stems), but at the top of the compression stroke (where it sparks), both valves are closed and both cams are completely out of the way. __________________ 2005 "Saturn Black", stock + tach Login or Register to Remove Ads
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08-31-2013, 11:40 PM	#106
Water Warrior 2 Senior Member Join Date: Dec 2006 Location: Squamish B.C Canada Posts: 11,409	Re: Tick tick clunk! Can't remember if this was asked before but here goes. Are you sure the cam shaft is syncronized with the crank? If you got it one tooth out on reassembly the valve timing would be out. You might never get the compression you need. Said my piece so now the rest of the guys can run with it if need be.
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09-02-2013, 01:22 PM	#108
Goose51683 Senior Member Join Date: Apr 2013 Location: Indiana Posts: 621	Re: Tick tick clunk! I've checked the TDC mark against the cam positioning more times than I can count. It appears my valves are closed when I hit that compression TDC mark as well. I'm checking valve gaps again today but I though I would pull the top and check the timing again for shits and giggle. Thanks for all the illustrations. Yet again the compression tester I got does not fit the bike so it looks like I have no choice but to order a specialty one to fit the 250. Being the holiday I won't be spending to much time on this but I'll let all of you know if I do find anything
	0

09-02-2013, 01:36 PM	#109
Goose51683 Senior Member Join Date: Apr 2013 Location: Indiana Posts: 621	Re: Tick tick clunk! Looking at the cam and lifters. Because the lifters ride on top of the cam I would want my lobes facing off or down at the TDC of the compression stroke right? So would this be 180 off
	0

09-02-2013, 06:29 PM	#110
alantf Senior Member Join Date: Nov 2008 Location: Tenerife (Spain) Posts: 3,719	Re: Tick tick clunk! Why not turn your photos to the correct position before posting them? makes things 100% easier for us. __________________ By birth an Englishman, by the grace of God a Yorkshireman.
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