Compression # on starting S&S 107?

[BadBrad]

If you do it my way, which is the CORRECT way, :argue: you can't go wrong. :2thumbs: You WILL get an accurate reading with the compression releases disconnected. Cold cranking is the favorite method hands down....
John

So, disconnect the CR, pull the plugs, full throttle, cold motor and turn it over till it peaks? Always good to know the "standard" method.

 

[Sven]

OcTizz My U Sea

If you do it my way, which is the CORRECT way, :argue: you can't go wrong. :2thumbs:

I'm not arguing the point. I described the book's abstract. Any other way is use is on use is own. Book may confuse some. Gotta breakout and breakdown the concept so you readabstracthiswaya dig?

Cold cranking is the favorite method hands down....
John

:roll: :2thumbs:

 

[Mojo]

Does anyone know what the compression # should be when cranking the 107 if the compression releases are working?

I had a new battery and starter installed and they tested the compression. They believe the compression releases are working.

The compression was 130#.

Any ideas???

Around 150 with compression releases plugged in, and wide open throttle. Around 170-175 with them disconnected. Easy way to check compression releases is to put your finger on top of them and push the start button. If you feel it pull down, then it is most likely working. If it pulls down more than 1 time while cranking, there is a problem. For those who cannot reach them, disconnect the starter solenoid wire and push the start button. If you hear a solid click in both the front and rear head, they are most likely working. I have yet to see one that was clogged or damaged that still worked. If you are concerned that the port in the head for the compression releases may be clogged at that point, do a compression test with them disconnected and see if it goes up. If they were working, then a leak down test would be in order if it still seems low. As for the discussions about what the hot/cold/ readings should be, valves and rings will seal either way unless there is a problem, and the readings should be somewhat close. If you squirt oil in the cylinder and the compression comes up considerably, you may have a ring problem.

P.S. I prefer a cold engine, and perform the intial compression test with the releases disconnected.

 

[MARV]

Just remember the releases are only activated for about a second on the newer BD's.

So probably tough to see on a comp test.

 

[Nukeranger]

One way to reduce the number of headaches is to listen to John and don't read what Sven writes!

 

[Brew]

I second that motion...

 

[TomM]

I third it!

 

[Th3InfamousI]

Holy hell. I'm thinking of just selling the bike because it's not worth the headache. :lol:

If you want to sell a bad engine dog, I'll buy

But I would advise that if your mechanic doesn't know what type of compression he should have on these engines then I'm not sure he should be your mechanic and trust his opinion.

 

[ksmike]

Just for grins I check my cold cranking compression again last night. Right around 192, both cylinders. 2010 Bulldog, 111, stock, 2,500 miles.

I thought that a brilliant point that Mojo made was to unhook the starter wire to check the energizing of the compression releases. They pull in for just about a second. :up:

And by the way, the difference between checking compression at closed throttle and WOT is about 60 psi on my bike (60 lower at closed throttle)