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Author Topic: Decompressor woes  (Read 1112 times)

Mr.Mazza

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Decompressor woes
« on: April 21, 2014, 09:26:47 PM »
In a nutshell, decompressor wont seal so I have no compression.
Long story: I was fiddling and dropped the valve into the cylinder, 4 hours later I got it out (at 11pm) so I reassembled the decomp unit, screwed it in by using a socket to push it down while twisting, otherwise I couldn't start the thread.
All good I thought, went to start her this morning, no comp and it weezed through the decomp, so Im a little up shit creek without a boat.
Do I have to put new washers, more or sealant? I need the bike running asap
Lizzy - 07 500 Deluxe ES - Red and chrome

ace.cafe

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Re: Decompressor woes
« Reply #1 on: April 21, 2014, 09:42:31 PM »
Typically, a decomp leak is most often the result of incorrect assembly of the decomp stack. It is very easy to get it wrong, and a lot harder to get it right. I suggest looking at a close-up photo of one which is known to be correct, and compare the assemblies.
Most often, this will find the problem, and proper reassembly will cure it.

It is rare that the decomp actually leaks due to a bad seal or a burned seal. If this is the case, then lapping the decomp valve like a regular valve and seat can cure it.
However, that is almost never the problem.
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ERC

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Re: Decompressor woes
« Reply #2 on: April 21, 2014, 09:43:18 PM »
You definitely need new washers. Also a good idea to use hi temp silicone around them. When you put it back in use a 13/16 spark plug socket so the valve sticks through the hole and use an open end or box wrench on the socket.  ERC
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azcatfan

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Re: Decompressor woes
« Reply #3 on: April 21, 2014, 09:53:24 PM »
Typically, a decomp leak is most often the result of incorrect assembly of the decomp stack. It is very easy to get it wrong, and a lot harder to get it right. I suggest looking at a close-up photo of one which is known to be correct, and compare the assemblies.
Most often, this will find the problem, and proper reassembly will cure it.

Here's alook at mine...



-2002 Bullet ES Up-Jetted with Ace Air Canister and punched HD Exhaust.

Mr.Mazza

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Re: Decompressor woes
« Reply #4 on: April 22, 2014, 12:12:05 AM »
Hmm seems I might be missing the main washer, would that cause a bad seal?
Otherwise it's properly assembled.

Also is it bad that I could completly remove the valve itself from the head?
Lizzy - 07 500 Deluxe ES - Red and chrome

ace.cafe

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Re: Decompressor woes
« Reply #5 on: April 22, 2014, 12:15:43 AM »
Hmm seems I might be missing the main washer, would that cause a bad seal?
Otherwise it's properly assembled.

Also is it bad that I could completly remove the valve itself from the head?

If the washer wasn't there, and the decomp wasn't fully seated, that might leak enough to cause issues.
And yes, you can remove the whole thing from the head, but you'll need a blanking plug, which was available at one time from Nfield Gear, and it might still be available. If you blank off the decomp, you'll need to use moderate foot pressure to slowly get the leakdown pressure past your rings to get the piston to TDC for kickstarting it. But it can be done like that.
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Mr.Mazza

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Re: Decompressor woes
« Reply #6 on: April 22, 2014, 12:19:24 AM »
If the washer wasn't there, and the decomp wasn't fully seated, that might leak enough to cause issues.
And yes, you can remove the whole thing from the head, but you'll need a blanking plug, which was available at one time from Nfield Gear, and it might still be available. If you blank off the decomp, you'll need to use moderate foot pressure to slowly get the leakdown pressure past your rings to get the piston to TDC for kickstarting it. But it can be done like that.

Ill try some washers then.
I meant is it a problem if I can physically remove the valve, shouldnt it be wider that its hole?
Lizzy - 07 500 Deluxe ES - Red and chrome

ace.cafe

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Re: Decompressor woes
« Reply #7 on: April 22, 2014, 12:29:20 AM »
Ill try some washers then.
I meant is it a problem if I can physically remove the valve, shouldnt it be wider that its hole?
It's the same thread size as the spark plug. Use a spark plug crush washer.
If you unscrew the whole thing from its base, it will come right out. Don't pull the cotter pin!
If you do take it out and don't have the proper blanking plug, there will be a small hole open there which connects into the exhaust port and you'll have an exhaust leak there. That's where the decomp vents into the exhaust port.
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Mr.Mazza

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Re: Decompressor woes
« Reply #8 on: April 22, 2014, 02:56:21 AM »
I did take the cotter pin out, this is why I had to do this in the first place :(
Could I use a spark plug with a thread sealer as a temp solution if i cant fix the decomp? Or until a replacemenf can arrive?

And would no decomp work with a hi-comp engine?
« Last Edit: April 22, 2014, 03:14:27 AM by Mr.Mazza »
Lizzy - 07 500 Deluxe ES - Red and chrome

ace.cafe

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Re: Decompressor woes
« Reply #9 on: April 22, 2014, 03:17:42 AM »
I did take the cotter pin out, this is why I had to do this in the first place :(
Could I use a spark plug with a thread sealer as a temp solution if i cant fix the decomp? Or until a replacemenf can arrive?

If you can find a spark plug small enough to fit in there, fine.
The boss around the hole usually won't fit a spark plug in there, but you might be able to find a small bodied spark plug.
The issue at that point would be the exhaust leak at the dump hole.
You could probably plug that temporarily with some silicone sealer. Silicone sealer might fix your decomp leak too, but you have to let it dry for the full 24 hours before you start up the engine. Otherwise it will blow out.
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Mr.Mazza

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Re: Decompressor woes
« Reply #10 on: April 22, 2014, 08:28:21 AM »
God damn it.
Its stripped, the thread is fucked.
Looks like the head's gotta come off, sent off, fixed and I'm bikeless for awhile, there goes my good mood for a long time.
Lizzy - 07 500 Deluxe ES - Red and chrome

Blltrdr

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Re: Decompressor woes
« Reply #11 on: April 22, 2014, 03:16:09 PM »
That is a tough one to chew on Mazza!

Well this is part of evolving as a human. When I was your age I f'd up something on a daily basis because I had little to no patience. I can't say I don't f up stuff any more, but the frequency is a light years difference from those younger years.

It is definitely a huge bummer because you just bought this bike and had been so excited about owning one for such a long time. The other thing that sucks when you are younger is the observance of time. http://ubiquity.acm.org/article.cfm?id=1455706
Everything seems to move so slow, takes forever to happen. When you get older you wish you could slow everything down a bit. Maybe things have changed as our world shrinks more and more because of technology, but it most likely is or feels the same way.

Learn from this and move on. Hopefully this is not your only transportation, that would really bite.

You should be able to find a local shop to helicoil the head for you. Not to hard of a repair. Everyone here will definitely give you a hand to get you back on the road again. Just remember to take your time and if you run into a problem, think it over or ask for suggestions before you tackle it. You don't want to snowball this thing and create more problems while trying to fix just one.
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Phlakaton

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Re: Decompressor woes
« Reply #12 on: April 22, 2014, 03:29:37 PM »
I feel your pain.  I have been on the hook learning how to do all my maintenance myself since the shop here in Austin doesnt sell or service REs anymore.  My decomp lever has been stuck and non-operational for a year - I just let the pressure out by hand to hit TDC before I kick her over.  I suppose I'll get to fixing it in your honor since you're out of commission.  Sucks man.  For some reason that thing scares me.  haha.
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cafeman

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Re: Decompressor woes
« Reply #13 on: April 22, 2014, 04:55:49 PM »
God damn it.
Its stripped, the thread is fucked.
Looks like the head's gotta come off, sent off, fixed and I'm bikeless for awhile, there goes my good mood for a long time.

Can you see down in the hole with a flashlight? Maybe remove the tank if not. There may be some good threads at the very end of the hole. Take some measurements and source a bolt no longer than the overall depth (or reuse the washers etc to get the required depth) You may be able to just catch the remaining good threads in the head? So long as the bolt doesn't protrude into the chamber. I just did this for an oil line banjo bolt hole that I stripped. Made a new longer banjo bolt to catch the good remaining threads in the hole. May work similar for you. Good luck ;)
« Last Edit: April 22, 2014, 04:57:54 PM by cafeman »

ERC

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Re: Decompressor woes
« Reply #14 on: April 22, 2014, 07:24:04 PM »
Heli-coil it with the head in place.  ERC
2-57 Apaches, 2-57 Trailblazers, 60 Chief, 65 Interceptor, 2004 Bullet, 612 Bullet chopped.