Port Timing Question

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marky2strk
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Port Timing Question

#1 Post by marky2strk » Fri Nov 11, 2011 11:19 pm

Hi All,

I just bolted up my rear cylinders that have been re-sleeved by LA Sleeve. I noticed that all ports on the rear cylinders open significantly earlier than the fronts. I cannot say precisely how much, because I don't have a degree wheel, but I would say several degrees. The pictures show cyl # 1 exhaust port just as cyl #4 is about to open.
I am sure that the drive gears are aligned correctly on the clutch because piston pairs reach TDC at the same time i.e. 1,4 & 2,3.

I know that the rear crank has different slightly different timing, but can anyone tell me if this port timing difference existed on new bikes from the factory? Will this much port timing difference lead to performance problems or failures down the road ?

When I bought this particular bike, the motor had been rebuilt at least once and I never disassembled my new bike I bought in 1984, so I have not seen the internals of a completely stock motor.

Any input appreciated.

Image

Image

Luther
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#2 Post by Luther » Sat Nov 12, 2011 3:52 am

Heres one way to check some things. Measure how far down the piston in the second picture is then rotate crank so the other piston is same position exhaust just opening and measure to see if its the same. I think stock is 26.5mm down. Its in the TSI post. Open the hole on the ignition cover and there should be 2 timing marks. I'm not sure how many degrees apart they are but it will give an idea how much 3 degrees is. Mine was a little less than that off. Stock piston pin offset is .5mm but I don't think changing it makes much difference.

vma500
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#3 Post by vma500 » Sat Nov 12, 2011 4:14 pm

that means you ve crank offset , since your upper ports open earlier your rear crank is more advanced thus has retarded ignition vs front

what engine nr ? 52x -51x ? canadian RZ or jap RZV

yes piston-offset with standard pistons = about 0.5mm
my bikes :RD500 2X ,RD 350 F2 , RD 350 31K,RD350 4LO,RG500,RG250 WW,RGV250,TZR250 3MA,TZR250 3XV,NS400r,NSr250 mc21,KR1250S,

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Gary Papesh
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#4 Post by Gary Papesh » Mon Nov 14, 2011 12:08 am

If you would like, I will e-mail you this file. Then print it, glue it onto some sheet metal or card stock, and Voila, instant degree wheel. [img][img]http://i93.photobucket.com/albums/l74/g ... ewheel.jpg[/img]
Sincerely, Gary P. [/img]
The man who dies with the biggest carbon footprint WINS !!!

marky2strk
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#5 Post by marky2strk » Mon Nov 14, 2011 2:40 am

Hi All,

Here's what I have found out:

I should not drink beer while working on my RZ !

It seems I was rotating the cranks the wrong direction. Clutck basket shoud rotate counterclockwise when the cranks are rotating in their normal clockwise direction. If you rotate the works in the opposite diection- it makes it appear that the rear ports are opening early. Rotate then in the correct direction and the ports open simultaneously. MAGIC !

Thanks for the replies anyway !

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#6 Post by vma500 » Mon Nov 14, 2011 3:17 am

what kind of beer did you drink .......please tell me all about ........cos we brew more then 800 sorts in our country but none has the effect you ve just described :smt017
my bikes :RD500 2X ,RD 350 F2 , RD 350 31K,RD350 4LO,RG500,RG250 WW,RGV250,TZR250 3MA,TZR250 3XV,NS400r,NSr250 mc21,KR1250S,

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aaronmvrider
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#7 Post by aaronmvrider » Mon Nov 14, 2011 3:23 am

sounds impossible... if the crank rotates backwards it should still be in same timing if rotated forwards... :shock: :shock:
my rides
rz 500 1984
2 x rz 350 1984
mv agusta f4 1000 2004

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Andrew
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#8 Post by Andrew » Mon Nov 14, 2011 10:50 am

aaronmvrider wrote:sounds impossible... if the crank rotates backwards it should still be in same timing if rotated forwards... :shock: :shock:
Agreed.


But still tell us where you buy your beer :grin:


On another note... I see you have a piston with a 1.00 marked on the crown. I thought this means it's on a 1mm bigger diameter (4th stage rebore)
I thought if you resleve your cylinder, it would go back to standard bore???
Did I think this while drinkning beer??? :grin:
Andy (UK)
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Faster Faster !!!

marky2strk
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#9 Post by marky2strk » Mon Nov 14, 2011 1:09 pm

Hi Guys,

We brew a lot of beer in California also, but I can't remember what I was drinking that particular evening ( that's the problem !).

As for the pistons, I am running stock size OEM pistons in the rear cylinders and the fronts are 1.00mm over Pro-X. A little history: after a seizure on the #3 cylinder, I decided to have both rears re-sleeved so I could run windowed pistons. I've been told by many that the different size pistons font to rear will not be a problem.

I can't explain why the port timing appears to change when you spin the cranks backward. I too thought that it should be the same regardless of direction. If there is an engineer type out there that coud explain it, I would appreciate the education.

vma500
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#10 Post by vma500 » Tue Nov 15, 2011 11:30 am

hi Mark , no offence please

i should check your engine again if i were you , this is nt normal ,there s is some slack between the 2 cranks but not that much ,the anti lash gears will prevent most of it . if the fotos are correct then there s more then 2mm offset ,means more then 7-8 degrees differance in ignitiontiming wich can be the cause for seizing the rear bank regulary .Why did it seize ? cranks scored ? please tell us !

please use the degree wheel Gary posted on here ,glue it on a CD disk ,check if cranks are really 180° counterrotating .It can be corrected very cheap and with limited skills
BTW you did nt mention the first 3 enginedigits ? 47X,52X,51X .....X from worse :grin:

The late 1GE ,53g ,1GG does not seem to have the crank offset
anymore ......thus corrected and serviced by yamaha already
my bikes :RD500 2X ,RD 350 F2 , RD 350 31K,RD350 4LO,RG500,RG250 WW,RGV250,TZR250 3MA,TZR250 3XV,NS400r,NSr250 mc21,KR1250S,

marky2strk
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Location: West Sacramento, CA

#11 Post by marky2strk » Tue Nov 15, 2011 10:41 pm

VMA500,

No problem.

My bike is a 47X Canadian model - last 5 digits on the VIN are 00477.

The seizure was related to a reed valve coming loose and causing a lean condition. There wasn't any crank damage.

It would be interesting to see if someone else could reproduce what I am observing if they have an engine with both heads off sitting around.

Luther
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Re: Port Timing Question

#12 Post by Luther » Wed Nov 16, 2011 1:04 am

marky2strk wrote:

I am sure that the drive gears are aligned correctly on the clutch because piston pairs reach TDC at the same time i.e. 1,4 & 2,3.

Will this much port timing difference lead to performance problems or failures down the road ?

When I bought this particular bike, the motor had been rebuilt at least once

Any input appreciated.

quote]

Me, i'd pull the clutch cover and see whats up. There shouldn't be hardley any backlash in the primary gears. They have to line up just right for the clutch to slide on. Yours looks off more than normal and the other side of tdc.

An offset key to fix the rear is a good idea.

If its been rebuilt thats even more reason to have a look.

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#13 Post by vma500 » Wed Nov 16, 2011 4:12 pm

Me, i'd pull the clutch cover and see whats up. There shouldn't be hardley any backlash in the primary gears. They have to line up just right for the clutch to slide on. Yours looks off more than normal and the other side of tdc.

An offset key to fix the rear is a good idea.

If its been rebuilt thats even more reason to have a look
aye Luther ,the pics from Mark shows exactly how far the cranks and port-timing can be out sync even with aligned marks , all the 47X engines are that worse , it s not just 4° out .....for correction offset key.... yes

Mark , i will scan and PM you the copys for the correction this weekend .....it s an easy mod you just need to fab a stepped key and time it a little differant (collet methode ) just have to find a good copier :grin:
my bikes :RD500 2X ,RD 350 F2 , RD 350 31K,RD350 4LO,RG500,RG250 WW,RGV250,TZR250 3MA,TZR250 3XV,NS400r,NSr250 mc21,KR1250S,

marky2strk
Posts: 46
Joined: Wed Jun 28, 2006 9:24 pm
Location: West Sacramento, CA

#14 Post by marky2strk » Thu Nov 17, 2011 1:49 am

Hi Guys.

Thanks for the input.

I have a question: if the port timing appears to be normal when turning the engine in its normal operating direction, why should I be concerned if timing is off in the reverse direction? It will never run in this direction.

Luther
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#15 Post by Luther » Thu Nov 17, 2011 2:14 pm

Hi Mark, Were here to help. I'm not a degreed engineer but after 35 years building machines for them I think I qualify.

What you describing can't happen unless parts are loose missing or assembeled wrong. When I made an offset key I was checking TDC with 2 dial indicators, one in a front head the other in a rear. When I got to .02" offset on the key both pistons move the same. Even at more than 1/2" down when the indicators ran out of stroke they are the same. turning cranks forward and backwards they are the same.

All the info you need is here in this post. Gary made a degree wheel, vma has documentation for different years offset errors, the other guys are backing up this info. The sticky post on crank timing is at the top of the list. You need to take clutch cover off and have alook. Maybe you have missmatched years of parts. have someone else read all this and look at it. Give us a picture of gear marks at TDC. If you give the info we need I'll make the offset key and mail to you.

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