Saito 450 overhaul
11-07-2004, 03:01 PM
#1
Thread Starter
My Feedback: (4)
Join Date: Dec 2001
Location: Dayton, OH
Posts: 358
Likes: 0
Received 0 Likes
on
0 Posts
Saito 450 overhaul
I am in the process of rebuilding my 450 triple due to a grinding noise in the bearings. Before disassembling the engine i thought i should make an accurate map of the valve timing. Here's what i came up with:
intake opens@ 38deg BTDC
intake closes@ 66deg ABDC
intake duration= 284deg
exhaust opens@ 65 deg BBDC
exhaust closes@ 35 deg ATDC
exhaust duration= 280deg
valve overlap= 73deg.
Pretty wild cam huh!
That valve overlap is extreme. I checked my harley performance catalog and the wildest cam offered by HD only has 52 degrees of valve overlap.
I have had problems in the past with the number 2 cylinder on my 450 dropping out. It didn't occur to me until i studied the valve timing chart but i'm guessing now that the valve overlap on this engine is so wild that the plugs are being put out out by the cold intake mixture blowing across them on its way out the exhaust. The 73deg. overlap i quoted above is for number 1 cylinder. Number 2, in my case the one that is hard to keep light has an overlap of 83 deg.
This difference is due i suspect to the large effect that the clearance between the rocker arm and valve stem has on the timing. Playing around with this clearance shows that a change of .002" equals 5 degrees of crank rotation. When this is applied to the valve timing numbers this same .002" now changes the valve overlap by 10 degrees.
Right now it is only my theory that the large valve overlap is wreaking havoc on the glow plugs job. When i get the engine back in operation i'm going to try opening up the valve clearance to see if this has any affect on number 2 cyl. dropping out.
intake opens@ 38deg BTDC
intake closes@ 66deg ABDC
intake duration= 284deg
exhaust opens@ 65 deg BBDC
exhaust closes@ 35 deg ATDC
exhaust duration= 280deg
valve overlap= 73deg.
Pretty wild cam huh!
That valve overlap is extreme. I checked my harley performance catalog and the wildest cam offered by HD only has 52 degrees of valve overlap.
I have had problems in the past with the number 2 cylinder on my 450 dropping out. It didn't occur to me until i studied the valve timing chart but i'm guessing now that the valve overlap on this engine is so wild that the plugs are being put out out by the cold intake mixture blowing across them on its way out the exhaust. The 73deg. overlap i quoted above is for number 1 cylinder. Number 2, in my case the one that is hard to keep light has an overlap of 83 deg.
This difference is due i suspect to the large effect that the clearance between the rocker arm and valve stem has on the timing. Playing around with this clearance shows that a change of .002" equals 5 degrees of crank rotation. When this is applied to the valve timing numbers this same .002" now changes the valve overlap by 10 degrees.
Right now it is only my theory that the large valve overlap is wreaking havoc on the glow plugs job. When i get the engine back in operation i'm going to try opening up the valve clearance to see if this has any affect on number 2 cyl. dropping out.
11-07-2004, 03:52 PM
#2
Senior Member
My Feedback: (3)
Join Date: Nov 2002
Location: Mary Esther, Florida, FL
Posts: 20,205
Likes: 0
Received 15 Likes
on
14 Posts
RE: Saito 450 overhaul
Bob:
All model four stroke engines have radical cam timing, that's where they get the power to rival the two stroke engines.
I posted the Saito valve timing for several different engines, if you look at that post your FA-450 R3 has three of the "Standard" 120/150/180 cam shafts, the timing numbers apply.
I have also made several posts about balancing the cylinders on a multi, and you have come on the correct method either by intelligent analysis, or blind luck. Reading your post it looks more like thought was the source.
Yes, cylinder balance is done by careful adjustment of the valves.
Bill.
All model four stroke engines have radical cam timing, that's where they get the power to rival the two stroke engines.
I posted the Saito valve timing for several different engines, if you look at that post your FA-450 R3 has three of the "Standard" 120/150/180 cam shafts, the timing numbers apply.
I have also made several posts about balancing the cylinders on a multi, and you have come on the correct method either by intelligent analysis, or blind luck. Reading your post it looks more like thought was the source.
Yes, cylinder balance is done by careful adjustment of the valves.
Bill.
12-07-2004, 06:23 PM
#3
Junior Member
Join Date: Nov 2002
Location:
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
RE: Saito 450 overhaul
I just assembled my Saito 450 and still have a doubt about the correct firing order. Regardless of what Saito have in their supplement manual for the 450, if I look at the engine from the front I name the top cylinder #1 and going counterclockwise the next cylinder is #2 and #3 next. Considering this, is the firing order 1,2,3 or 1,3,2?
I will appreciate your help!!!!!
I will appreciate your help!!!!!
12-07-2004, 06:50 PM
#4
Senior Member
My Feedback: (3)
Join Date: Nov 2002
Location: Mary Esther, Florida, FL
Posts: 20,205
Likes: 0
Received 15 Likes
on
14 Posts
RE: Saito 450 overhaul
Pat:
Your numbering order is correct for a radial engine.
Firing order? Since the engine has separate cams for each cylinder it can be set up 1-2-3 or 1-3-2 as you wish. The correct order is 1-3-2 because 1-2-3 will give uneven firing intervals.
With the "Wrong" order the power will be down also, as the single carb is sized to feed one cylinder at a time. If two are drawing together, as will happen with uneven intervals, they are fighting each other for the fuel/air mixture and neither gets as much as it would otherwise.
Bill.
Your numbering order is correct for a radial engine.
Firing order? Since the engine has separate cams for each cylinder it can be set up 1-2-3 or 1-3-2 as you wish. The correct order is 1-3-2 because 1-2-3 will give uneven firing intervals.
With the "Wrong" order the power will be down also, as the single carb is sized to feed one cylinder at a time. If two are drawing together, as will happen with uneven intervals, they are fighting each other for the fuel/air mixture and neither gets as much as it would otherwise.
Bill.
12-07-2004, 07:56 PM
#6
Senior Member
My Feedback: (3)
Join Date: Nov 2002
Location: Mary Esther, Florida, FL
Posts: 20,205
Likes: 0
Received 15 Likes
on
14 Posts
RE: Saito 450 overhaul
Patricio:
Don't bother reading this one, it's a copy of the email I just sent you. Decided to post it also, it might help someone else.
Bill.
Don't bother reading this one, it's a copy of the email I just sent you. Decided to post it also, it might help someone else.
Pat:
I'm sure you know what the "Overlap" point is with the valves.
Pull all six rocker covers and the glow plugs, turn the crank to maximum overlap on #1. Stick a tooth pick or something similar in the plug hole to be sure it's at TDC.Fasten a prop on loosely, with one blade pointed directly at #1. Now turn the prop counter clockwise 240 degrees, until the same blade is now in line with #3 cylinder. #3 should now be at max overlap. Another 240 degrees and #2 should be at max overlap. 240 degrees more should have you back at the overlap point on #1. If you find max overlap on any cylinder is not at TDC of the particular cylinder, that one cam is out of time.
The timing gear teeth are coarse enough that even a one tooth error will be obvious.
Hope this helps.
Bill.
I'm sure you know what the "Overlap" point is with the valves.
Pull all six rocker covers and the glow plugs, turn the crank to maximum overlap on #1. Stick a tooth pick or something similar in the plug hole to be sure it's at TDC.Fasten a prop on loosely, with one blade pointed directly at #1. Now turn the prop counter clockwise 240 degrees, until the same blade is now in line with #3 cylinder. #3 should now be at max overlap. Another 240 degrees and #2 should be at max overlap. 240 degrees more should have you back at the overlap point on #1. If you find max overlap on any cylinder is not at TDC of the particular cylinder, that one cam is out of time.
The timing gear teeth are coarse enough that even a one tooth error will be obvious.
Hope this helps.
Bill.
