The Mechanical (centrifugal) Advance

[3Phase]

Yes, please!

You still need a 78 E governor?(mechanical advance)? I can pull one from my spare motor.

Actually, yes, I do!

I was going to weld up one of the '79 or '80 Reluctors and regrind the advance slots if I couldn't find a '78E advance.

I can't easily change the advance curve but I'm toying with the idea of setting the Base timing to ~10 degrees and using one spring from the '80G advance and one from the '79 to get the timing all-in sooner. This is supposed to be fun so I really don't want to go too far past the upper advance limit with pump gas and break or melt ... stuff.


I had to take a break to go pick up some sealer from the dealer because my tube of Yamabond 4 turned into a little gray hockey puck. The parts dept. claims that Yamabond 4 is backordered until September and all they had was some Threebond 1207B for twenty bucks! "Uh, pardon me, there's just one more thing...."

A-A-A-I-I-I-E-E-E! Give me a call or shoot a PM.

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[3Phase]

REPOST: The Mechanical (centrifugal) Advance

Inspecting and servicing the mechanical advance is easy, it's just not as not as sexy as triple cleaning the carburetors. It's also very messy but it's necessary or the mechanical advance will eventually die.

Please note that the cracked mechanical advance in these pictures is from Bush, my salvaged '79 Special, not from Columbo, my 1980G!


MechAdv1: The XS1100 mechanical advance assembly ready to be serviced with the snap ring removed. All 1978 to 1980 Yamaha XS1100s have a movable reluctor mounted on a shaft with spring-loaded weights.

MechAdv1.jpg



MechAdv2: The XS1100 reluctor with its inner grease reservoir that should be filled with high-temperature grease to lubricate the reluctor, the mechanical advance shaft and its bushings.

MechAdv2



MechAdv3: Fill the grease reservoir in the reluctor body with high temperature grease.

MechAdv3.jpg



MechAdv4 and MechAdv5: The XS1100 mechanical advance shaft and its bushings. The reluctor slides onto this shaft and the reluctor's slots engage the posts on the mechanical advance weights at the base of the shaft.

The upper bushing is fixed and does not move. The lower bushing rotates freely on the shaft. It can also move axially on the shaft below the upper bushing.

To grease the lower bushing and shaft, pack grease into the upper slot while turning the bushing to allow the grease to move between the shaft and the bushing. Move the bushing axially and pack more grease into the lower slot. Repeat as necessary until the grease has been worked in place between the bushing and the shaft, then reassemble the mechanical advance.

Unfortunately, this mechanical advance is junk but it can be stripped for parts. There is a large crack in the lower bushing from wear and fatigue caused by lack of lubrication and you can see the 'witness mark' left on the upper bushing by the reluctor's obviously empty grease reservoir.

MechAdv4.jpg


MechAdv5.jpg


MechAdv6: Before putting the snap-ring back on the shaft to hold the reluctor, make sure the reluctor tip aligns with the slot in the base of the mechanical advance shaft or the reluctor will be 180 degrees out of time.

MechAdv6.jpg


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[mack]

advance

Ok Scott, sit tight, I have to baby sit my grandson today so I won't get a chance to pull my spare motor parts today. What all do you want me to send. And I've lost your address, you'll need to PM me.

[mack]

Scott

I don't want to get your hopes up. I was told this motor was from an E but lets make sure. Check this serial number 2H7-100215

[BA80]

I don't want to get your hopes up. I was told this motor was from an E but lets make sure. Check this serial number 2H7-100215

That's an F VIN mack.

1978 XS1100E 2H7-000101 Macho Maroon
1979 XS1100F 2H7-020101 Magenta Red, Indigo Blue

[mack]

Well if

that's the case Scott, you won't be any farther ahead with what I have. Sorry man.

[mack]

Greg

You sure about that number, I just checked the one I'm working on and it's number is 2h7101419 and the sticker on the yoke says it was made 1/78. Too early to be making F's. Maybe because these numbers are Canadian?

[IanDMacDonald]

You sure about that number, I just checked the one I'm working on and it's number is 2h7101419 and the sticker on the yoke says it was made 1/78. Too early to be making F's. Maybe because these numbers are Canadian?

Only definitive way to know is to pull the advance. 2H7-10 should be stamped on the back.

[BA80]

Only definitive way to know is to pull the advance. 2H7-10 should be stamped on the back.

The 79's came out in like June of 78. The were way ahead of the year designation.

It is possible the Canadian model is a little different numbering.

Here's the numbers........ http://hitechkc.dyndns.org:78/phpbb3...d9d43704e34e55

[3Phase]

There is also a one-piece advance bushing, not the split two-piece design:-


MechAdv7.jpg


I'm not sure why but the direct [IMG] links stop working after a while and that's no good. Unless I can figure out how to find a permanent [IMG] link, so much for using Onedrive for image hosting. And it looked so promising too.

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[3Phase]

It's cool! Really!

Don't shred your spare engine!

I have several '79 and '80 mechanical advance assemblies. I'll work out a way to shrink the slots in one of the good reluctors so I can use '78 timing (or better) without toasting the engine.

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[mack]

Yes

the bike i'm working on has the one piece bushing. I'll pull the other and have a look for the 2h7-10 number and if the bushing is one piece. Don't give up hope yet Scott.

[mack]

I pulled

the governor out today and it really wasn't a big job. So it has 2H7-10 stamped on it's just like the one I'm working on ,so I don't know about serial number accuracy. Amyway Scott, if your looking for a 2H7-10 I can send u this one. PM me your address again, with everything u need and I'll make it so.

[3Phase]

You got it! Thanks, Mack!

I was just out in the garage going through my broken drill bit collection again looking for a 1/16" bit to use for limiting the length of the reluctor slots.

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[IanDMacDonald]

Looks like you and me both found one today Scott. Fellow forum member is sending me an "E" timing wheel, advance and vacuum pod.