Need help identifying the mechanical advance unit

[DrDoot]

I can't tell if this is a Nippon Denso mechanical advance, or a Kokusan brand. Marking should be either ND or KD, and I can't tell which. Any of you experts out there think you can tell?

Pics are posted at:
http://img.photobucket.com/albums/v490/gs1327/80%20GS550L/GS550advancerotherside.jpg
and

http://img.photobucket.com/albums/v490/gs1327/80%20GS550L/GS550advancercloseup.jpg

and

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&sspagename=ADME%3AL%3ARTQ%3AUS%3A1&viewitem=&item=250035582654

Can't find any conclusive identification in old threads. Thanks much.

-RAY

[duaneage]

Looks identical to me..

[GS850_Coug]

Looks identical to me..

I think those are all pics of the same advance unit. He's wanting it identified before he bids, I believe.[-o<

[DrDoot]

Yes, all three links are for the same unit, just need to know whether it's Kokusan or Nippon Denso.

[earlfor]

I dont think there were any kokosan advance units. They were all ND.
It would not matter anyhow as all crankshafts had the same indent slot for the advance unit to mate into, so they would have to be the same. The KD vs ND ignition question only applies to the breaker plate. The mount holes for the point sets are different spacing on KD and ND setups. Either plate will fit the mechanical advance unit.

E.

[SqDancerLynn1]

Their is a difference as to where the timing marks are

[rkubik]

service manual should say

Check the book for a 550, but in the Clymer manual for the 650s, it says the chain drive models use Kokusan ignition while the shaft drive models (of the L model is one) use Nippon Denso.

[DrDoot]

While it seems the mechanical advance units from older 550 bikes would be compatible with the '85 model, would larger engine sizes have the same mechanical advance size as smaller engine sizes? Most likely? Such as from a GS850... I found one that looks identical but I don't know if the size would be different.

[earlfor]

Their is a difference as to where the timing marks are

Thats interesting. Yeah really. :-) Not having measured the timing marks on all GS models, I can only speculate. Considering all four cylinder GS models have the same crankshaft throws, then the only viariable for timing marks would be rpm range. Some models do have a slightly higher redline than others, so technically, the full advance marks could be slightly different. The static timing marks should not be since advance required is a function of rpm. (and yes heat and load, but to keep it simple :-) ) Anyway, considering the narrow range of upper rpm variance between GS models, the difference in max advance marks (if any) should be slight to nil. I will hazard a guess that if you set any GS four cylinder to 32 deg max advance, it will run just fine. 32 deg BTDC BTW, is the point at which the firing sequence is initiated, not the crankshaft position when the air/fuel mixture explodes and exerts a force on the piston pushing it downwards. If combustion was completed at 32 deg BTDC, the engine would stop......ABRUPTLY. :-)

E.

Earl

[SqDancerLynn1]

All of the advance units are interchangeable, as i said timing marks are different. Checked my parts bin difference is weather the advance unit is for points or elect ign setup

[earlfor]

All of the advance units are interchangeable, as i said timing marks are different. Checked my parts bin difference is weather the advance unit is for points or elect ign setup

Ahhh, the difference then would be due to lag time between points and electronic systems. Shouldnt be much.

E. :-)

[duaneage]

On most newer GS bikes the initial timing is not adjustable anyway. For example a 650 is 10 degrees before with 34 degrees of advance between 3400 and 3800 rpm. So the real issue would be does it naturally start out at 10 and will it advance the proper amount at the proper rpm. IF you have springs you could move them over to this unit and test it.