tboooe griff851 wroteHope this helpsThank you. The pics you provided are for an 888. The clearances for an 851 is the same?
MarkT I could not expand what Griff provided so I will give you what I set my 851’s and Corse motors. These are the early tighter specs. The later specs got looser and looser so I will give you both. Also, later on, the factory also gave you what they called checking specs which were the maximum clearance before you absolutely had to re-shim. Now this is very very important. The 851s before 1992 use the light Corse return springs so you cannot simply stuff in a feeler gauge and if it goes in you have the correct clearance. If you do that you will be setting both the opener and the closer way wrong because if you feel any drag/resistance on the feeler gage you are actually pushing open the valve Does this make sense— if not look at a diagram of how the desmo system works. By ’92 the factory installed much stiffer street closer springs to assure idle so you can set the clearances by feeling a firm drag on the feeler gage. because it was hard to overcome the closing spring pressure to open the valve. Your SP2 has the light springs so beware. I always pulled the heads on my SP2 and Corse bikes when setting the valves so I could put a dial gauge directly on the face of the valve so I would know I was opening the valve if I was checking with a feeler gauge that was too thick. If you do this job every day you could keep the heads on and use a slight touch. I assume that you do not wish to pull your heads so I would pull your throttle bodies and rear subframe to get plenty of clearance if this is your first time. OK. There are many ways to check clearances and if you do not pull the heads to measure valve movement a Dial gage, then many owners use the “stuff feeler gages in until you cannot stuff anymore" method to determine the closer clearance. This is how it goes for your SP2 Opener clearances do not require any “feel”- just good technique. If a feeler goes in with no resistance or drag that is the correct clearance. If you feel any resistance at all you are very close to opening the valve. I add or subtract .005 depending. If my correct feeler is a bit loose but I cannot install the next size up feeler gage without feeling drag then I subtract .005. If I feel even the slightest resistance I add .005 to my value. For the closer using the “stuff it” method, I push down the edge of the closing rocker with a small flat screwdriver and install feeler gages until you can no longer stuff in the next larger size feeler. Subtract the closer clearance you just measured from the opener clearance and that is the current closer clearance. There is always a bit of flex in the system so If you really jam in a thick feeler gauge, you should subtract about .001 from that number. Also, one trick to use—-when you have the maximum shim stuffed in—rotate the cam. If you cannot rotate it or you feel drag between the cam and the rocker arm, you are too tight and you need to subtract at least .005 from the closer shim you install. After you install the closer rotate the cam again and it should rotate freely. On the 851 and Corse I aim for .005 on the inlets and .006 for the exhaust openers, with .003-.005 for the closers. The first closer specs called for .002-.003 but that was hard on the rocker arms thus the .003-.005. So how do you go about this checking? First, you need a good micrometer to measure shims. Using one of the small aluminum 10mm (forget the actual length) shim stands helps you quickly measure them consistently. I use the factory dial gauge stand-but the after-market measuring stands work great with a good micrometer. I pull off the belts. ALWAYS stuff paper towels, or cotton balls down the oil return holes at the front ends of the heads. If you do not I can assure you that a half ring will jump down one of the holes and you will be praying that your tiny magnet will retrieve it. If you need to replace a closer cap you will need a rocker pin puller (street bikes can use a top removable cap thread of a spark plug) to move the rocker arm slightly to the side in order to pull the cam out for the installation. I also use a long thin screwdriver when removing a closer because I put it behind the closer rocker arm to lever/push it forward and hold it in that position. This relieves the pressure on the closer shim so you can remove it. Put the piston of the head you are working on at TDC so that when you remove a closer the valve will drop onto the top of the piston and not fall very far so you can bop it with a brass drive to pop off the closer shim. When installing a closer with new half rings, which often have a cut tail on each end that makes it hard to snap them into the valve stem keeper groove, you often have to use a stone to dress them. You often have to pry up on the closer shim to get them to pop into place. You will find the half rings are often broken into pieces which is a sign someone enjoyed revving the snot out of the bike—or never changed to new half rings the last time the valves were gone over. Here is the important thing to check after you think you have seated the new closer shim correctly. When correctly snapped up, the top of the valve stem and the closer top surface should feel almost flush with each other. If they are not then the half rings are not seated correctly. After a few times, you will know what I am talking about. After you get the closer shim snapped up correctly a few times you will know just by the snap feel as well as the flush-to-stem top feel if the half rings are seated. Now here are the Looser valve setting and Checking specifications. I only use these as a reference on the 851 or Corse bikes in case I do not have the correct shim in my kit to set to my preferred tight specs, or if I do not wish to lap grind a good larger shim. Setting Opening. Intake. .005–007. Exhaust. .007—.009 Closing. Intake. .005–.007. Exhaust. .003—.005 Checking Opening. Intake. .002—.07. Exhaust. .002-.009 Closing. Intake. .005—.010. Exhaust. .003—.008 OK— I am sure I have confused you enough and Griff will have to come in a perform triage to save you from my poor instructions.
MarkT Sorry--- this new system does not allow me to make paragraphs. Even though they were there when I wrote this. I could not expand what Griff provided so I will give you what I set my 851’s and Corse motors. These are the early tighter specs. The later specs got looser and looser so I will give you both. Also, later on, the factory also gave you what they called checking specs which were the maximum clearance before you absolutely had to re-shim. Now this is very very important. The 851s before 1992 use the light Corse return springs so you cannot simply stuff in a feeler gauge and if it goes in you have the correct clearance. If you do that you will be setting both the opener and the closer way wrong because if you feel any drag/resistance on the feeler gage you are actually pushing open the valve Does this make sense— if not look at a diagram of how the desmo system works. By ’92 the factory installed much stiffer street closer springs to assure idle so you can set the clearances by feeling a firm drag on the feeler gage. because it was hard to overcome the closing spring pressure to open the valve. Your SP2 has the light springs so beware. I always pulled the heads on my SP2 and Corse bikes when setting the valves so I could put a dial gauge directly on the face of the valve so I would know I was opening the valve if I was checking with a feeler gauge that was too thick. If you do this job every day you could keep the heads on and use a slight touch. I assume that you do not wish to pull your heads so I would pull your throttle bodies and rear subframe to get plenty of clearance if this is your first time. OK. There are many ways to check clearances and if you do not pull the heads to measure valve movement a Dial gage, then many owners use the “stuff feeler gages in until you cannot stuff anymore" method to determine the closer clearance. This is how it goes for your SP2 Opener clearances do not require any “feel”- just good technique. If a feeler goes in with no resistance or drag that is the correct clearance. If you feel any resistance at all you are very close to opening the valve. I add or subtract .005 depending. If my correct feeler is a bit loose but I cannot install the next size up feeler gage without feeling drag then I subtract .005. If I feel even the slightest resistance I add .005 to my value. For the closer using the “stuff it” method, I push down the edge of the closing rocker with a small flat screwdriver and install feeler gages until you can no longer stuff in the next larger size feeler. Subtract the closer clearance you just measured from the opener clearance and that is the current closer clearance. There is always a bit of flex in the system so If you really jam in a thick feeler gauge, you should subtract about .001 from that number. Also, one trick to use—-when you have the maximum shim stuffed in—rotate the cam. If you cannot rotate it or you feel drag between the cam and the rocker arm, you are too tight and you need to subtract at least .005 from the closer shim you install. After you install the closer rotate the cam again and it should rotate freely. On the 851 and Corse I aim for .005 on the inlets and .006 for the exhaust openers, with .003-.005 for the closers. The first closer specs called for .002-.003 but that was hard on the rocker arms thus the .003-.005. So how do you go about this checking? First, you need a good micrometer to measure shims. Using one of the small aluminum 10mm (forget the actual length) shim stands helps you quickly measure them consistently. I use the factory dial gauge stand-but the after-market measuring stands work great with a good micrometer. I pull off the belts. ALWAYS stuff paper towels, or cotton balls down the oil return holes at the front ends of the heads. If you do not I can assure you that a half ring will jump down one of the holes and you will be praying that your tiny magnet will retrieve it. If you need to replace a closer cap you will need a rocker pin puller (street bikes can use a top removable cap thread of a spark plug) to move the rocker arm slightly to the side in order to pull the cam out for the installation. I also use a long thin screwdriver when removing a closer because I put it behind the closer rocker arm to lever/push it forward and hold it in that position. This relieves the pressure on the closer shim so you can remove it. Put the piston of the head you are working on at TDC so that when you remove a closer the valve will drop onto the top of the piston and not fall very far so you can bop it with a brass drive to pop off the closer shim. When installing a closer with new half rings, which often have a cut tail on each end that makes it hard to snap them into the valve stem keeper groove, you often have to use a stone to dress them. You often have to pry up on the closer shim to get them to pop into place. You will find the half rings are often broken into pieces which is a sign someone enjoyed revving the snot out of the bike—or never changed to new half rings the last time the valves were gone over. Here is the important thing to check after you think you have seated the new closer shim correctly. When correctly snapped up, the top of the valve stem and the closer top surface should feel almost flush with each other. If they are not then the half rings are not seated correctly. After a few times, you will know what I am talking about. After you get the closer shim snapped up correctly a few times you will know just by the snap feel as well as the flush-to-stem top feel if the half rings are seated. Now here are the Looser valve setting and Checking specifications. I only use these as a reference on the 851 or Corse bikes in case I do not have the correct shim in my kit to set to my preferred tight specs, or if I do not wish to lap grind a good larger shim. Setting Opening. Intake. .005–007. Exhaust. .007—.009 Closing. Intake. .005–.007. Exhaust. .003—.005 Checking Opening. Intake. .002—.07. Exhaust. .002-.009 Closing. Intake. .005—.010. Exhaust. .003—.008 OK— I am sure I have confused you enough and Griff will have to come in a perform triage to save you from my poor instructions.
MarkT This new system is weird-- I cannot have paragraphs and when I make a change it posts everything again. That is why there are two impossible long single paragraphs that is a repeat. I am a moderator and I do not see the normal tools I have used in the past to straighten out this section. I cannot even see a preview.
tboooe Thank you Mark, I really appreciate your detailed reply. I have checked clearances on my 748 and 996 so I am familiar with the process, esp with making sure the half rings are fully seated into the shim. The bit about the soft opener spring in my SP2 I did not know about! One question, you mentioned that Checking values are the max ones before absolutely having to reshim. In your values below the Checking ones are actually higher on the low end and the same on the high end for Openers. Did I misunderstand? The Closer values are larger on the high end. Setting Opening. Intake. .005–007. Exhaust. .007—.009 Closing. Intake. .005–.007. Exhaust. .003—.005 Checking Opening. Intake. .002—.007. Exhaust. .002-.009 Closing. Intake. .005—.010. Exhaust. .003—.008
