Kzrider Member Needs Help ASAP with 1000 Rebuild

larrycavan wrote:

I thought you already checked the cam timing....

Why do guys put engines together without absolutely being certain the cams are in properly and then head back after experiencing problems to verify the cam timing?....:dry:

Engine building 101 - rule #1

Take the time to do it right....or make the time to do it over....<br><br>Post edited by: larrycavan, at: 2006/10/28 07:34

We put the jugs on and head on a couple of nights ago He (Barry) was going to put the cams, carbs etc. on tonight when he called me saying that the compression was still only around 75 lbs.

It was not Reborn650 that installed the cams, it was the other guy, sounds like Reborn650 has not seen the motor since the cams were installed.

The usual reason for not checking the timing to make sure it is correct is inexperience and not realizing that attention to detail is critical. Probably the guy's first rebuild and he's a little scared, and that's not unusual.

Next time he will know better

I'd list my past mistakes, but I don't want to type a 5000 word post

larrycavan wrote:

Not necessicarily.....in fact, over lapping of the valves is detremental to flow.

Agreed. Overdoing *anything* ain't good.

If you're using a lapping compound that is coarse enough to cut that much material, you're spoiling the benefits that a proper valve job could have provided to begin with.

I'll go for that. But then, some grinder operators are better than others. There are quite a few out there that'd be better employed hacking on pork chops down at the A&P.

A gentle lap with *light* compound will provide a visual indication of how wide and where on the valve lip/seat the actual seal is located.

I've never seen where mismtached seat/valve angles improve flow.

It has nothing to do with "mismatched angles." It has everything to do with sizing and locating the physical seat.

Turbulence generation is more of a function of port shape, surface irregularities and velocity mismatches than seat angle.

Agreed - to a point.

You keep coming back to "seat angles", and that has NOTHING to do with it - the offset angles are merely a conveinient device for locating and sizing the physical seat. If the location of the physical seat is not concentric with the axis of the valve stem, one side or the other will "unseat" first. It's a fact.

You can do all the porting and flowing in the world, but the valve/seat gap is the last link in the chain - the last obstruction to flow. There are gangs of guys from NASA down to NASCAR that study combustion chamber flow dynamics, and you can bet they've seen it.

In any event, I think we're way beyond the spec required by Colin's (ooops! sorry! ) friend.

I thought you already checked the cam timing....

Why do guys put engines together without absolutely being certain the cams are in properly and then head back after experiencing problems to verify the cam timing?....:dry:

Engine building 101 - rule #1

Take the time to do it right....or make the time to do it over

Agreed. Leakdown, cam timing, gasket check. One of those should fix the problem...

Post edited by: Pterosaur, at: 2006/10/28 10:37

Shit, had the whole message typed and hit the wrong button.
Hi all
Barry here. Thanks Colin and all u others.
I gotta start somewhere Larry. I was an apprentice the "firsttime", but that was a long time ago, very far away. I'll keep working at it till I get it right. (that's just me). Got this one guys, thanks, it turns out that I set the cams like the Clymer said, but it was out 180. Looked at the cams closely, rotated it, and compressions is now at about 120. yyyessssss.
I love machines. (as opposed to!!!) I guess that's why I have my tv and lazy boy in the garage. Colin, I'll make sure I have beer the next time.
Thanks all
Barry
(where's Ralph?)
:silly:

Another mystery solved by the crack KZR CSI Squad:) That's why I love this collection of mechanics, engineers, tinkerers and KZ-Phd. veterans.

Thanks gang.

Cheers-Colin

i wouuldve jumped in ,but i was busy making cookies for gris:whistle: you didnt bump any valves while you were spinning it with cams out of wack did ya?

wireman wrote:

i wouuldve jumped in ,but i was busy making cookies for gris:whistle:

And here I thought you wuz in your little white coat whacking poke' chops down at the A&P... :whistle:

Pterosaur wrote:

wireman wrote:

i wouuldve jumped in ,but i was busy making cookies for gris:whistle:

And here I thought you wuz in your little white coat whacking poke' chops down at the A&P... :whistle:

no i dont have to be there till 4pm:huh:

Pterosaur wrote:

You keep coming back to "seat angles", and that has NOTHING to do with it - the offset angles are merely a conveinient device for locating and sizing the physical seat. If the location of the physical seat is not concentric with the axis of the valve stem, one side or the other will "unseat" first. It's a fact.

I went back and reread your comments from before. Now I think I see what's happened here. I think you're not understanding the term "mismatched angles" properly.

I'm not talking about the usual 60/45/30 angles of a common 3 angle valve job with the seat and valve face both cut to 45*.

Mismatched angles are when the valve face and the seat are cut at differing angles like 44/46.

In situations where the seats have been cut like that 44/46, the immediate sealing effects are going to be reduced and lower compression on an initial compression test will result. Too many other factors [cam, spring, type of running, etc] come into play to be able to determine at what point the seating will be fully effective.

What I'm saying is that if you try to lap the valves with coarse compound to cure that situation, you're going to end up with wide and grooved seats. Both bad for flow.

FYI...those inside and outside angle choices play a lot bigger role in the final result of the flow dynamics than you give them credit for. There's a lot more to it than using them simply as seat angle locaters.

larrycavan wrote:

I went back and reread your comments from before. Now I think I see what's happened here. I think you're not understanding the term "mismatched angles" properly.

I'm not talking about the usual 60/45/30 angles of a common 3 angle valve job with the seat and valve face both cut to 45*.

Mismatched angles are when the valve face and the seat are cut at differing angles like 44/46.

We're essentially on the same page - the issue is terminology; what you're calling "mismatched angles" is what I call SCRAP.

What I'm saying is that if you try to lap the valves with coarse compound to cure that situation, you're going to end up with wide and grooved seats. Both bad for flow.

Totally agree.

FYI...those inside and outside angle choices play a lot bigger role in the final result of the flow dynamics than you give them credit for. There's a lot more to it than using them simply as seat angle locaters.

I'm well aware of that. Fluid dynamics has long been not only an area of interest, but of literally health & welfare to me. The details are unimportant.

As I recall, it was I that first mentioned the efficiency of valve seating as regards flow in the first place, so I'm not sure why you'd think the topic escapes me.

But for the purposes of the thread, I was trying to keep the issues in the realm of the applied problem.

. -30-

Secondtime wrote:

Shit, had the whole message typed and hit the wrong button.
Hi all
Barry here. Thanks Colin and all u others.
I gotta start somewhere Larry. I was an apprentice the "firsttime", but that was a long time ago, very far away. I'll keep working at it till I get it right. (that's just me). Got this one guys, thanks, it turns out that I set the cams like the Clymer said, but it was out 180. Looked at the cams closely, rotated it, and compressions is now at about 120. yyyessssss.
I love machines. (as opposed to!!!) I guess that's why I have my tv and lazy boy in the garage. Colin, I'll make sure I have beer the next time.
Thanks all
Barry
(where's Ralph?)
:silly:

That's cool and I wasn't picking on you or putting you down. I just see things like this all the time in forums.....

It wasn't long ago one poor guy had similar troubles and posted in another forum...swore the cams were in right...it wasn't until pics were posted of the head in which you could clearly see that every [brand new] exhaust valve had been bent from improperly installed cams. Why he turned the motor over after feeling resistance is beyond me....

In every step of engine assembly, take your time with everything you're doing. Check everything twice before you move on to the next component's assembly.

Post edited by: larrycavan, at: 2006/10/28 14:49

hey Larry. Thx bud. I'm going to heed that advice of going slow and checking, checking, checking. I just decided to take the entire bike apart to restore. It's in pretty good shape now, and won't take much but elbow grease. In the meantime I have to install another cam chain and piston, cause I chipped it taking it appart. Oh well, shit happens, and the winter is long here. I wonder how many beer Colin can drink? :lol:
Any thoughts on cleaning and polishing.

Barry

Thanks guys, i've calculated the distance from the earth to the sun. Now if i can just figure out how to get off the moon.