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| Author |
Message |
    
Michael Naujelis
New member
Username: naujelism
Post Number: 1
Registered: 04-2008
| | Posted on Monday, May 05, 2008 - 11:00 am: | 
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I have a 1976 Johnson 55, I am having trouble getting the idle to stay at one level. The mechanic that is working this issue has checked compression, spark and other things, he is now saying it could be the reids (SP?) not sure what that is, can you explain this? |
Elisha Danzig
Member
Username: zmasterflex
Post Number: 6
Registered: 04-2008
| | Posted on Wednesday, May 07, 2008 - 07:32 am: |
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This post is copied from yahoo.com answers:
If you go to How things work.com they have some good flashes that show how a 2 stk works. A reed valve allows air to be pushed in through the carb or throttle body in to the crank case when the piston is moving from BDC (bottom dead center) to TDC (top dead center) the end of this movement is the secondary compression stroke. This movement also allows the crankcase area to increase and the pressure decreases thus allowing air to be pushed into the crankcase past the reeds. As the prior air/fuel charge is ignited, the expanding nitrogen pushes the piston from TDC to BDC thus creating primary compression of the air fuel mixture in the crankcase. This will then push the air fuel mixture into the cylinder via the intake ports in the cylinder wall. The reed valves must seal the crankcase pressure or the mixture will be pushed back through the intake (carbs) and then "spitting" fuel outward. Reeds are a one way check valve,in a nut shell.
The running issue will vary as the degree of failure. Split or chipped reeds will cause a running issue at higher speeds, not too much a lower speeds. Broken peddle will cause low speed missing and no running at higher speeds. Weak reeds will make a motor run great at low speed but limit the rpms the motor will turn. A damaged reed will not cause a backfire, it can do what is known as a lean pop through the intake.
If you have an Optimax, different running issue, let me know.
To clear something else up, 2 stk motors control the crankcase pressure through, piston port, Reed valves or rotary valves. Reeds can either be plastic or metal |
Michael Naujelis
New member
Username: naujelism
Post Number: 2
Registered: 04-2008
| | Posted on Thursday, May 08, 2008 - 11:44 am: |
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thanks for the response, what do you think the repair cost on these reeds run? which is better, plastic or metal? do you have a source to purchase these parts?
thanks for the help |
ikia
Visitor
| | Posted on Thursday, May 08, 2008 - 12:07 pm: |
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The reeds are behind the carburetors ---remove carburetors and intake manifold ---easy do it yourself job. |
Joe Reeves
Senior Member
Username: joereeves
Post Number: 5985
Registered: 02-2001
| | Posted on Thursday, May 08, 2008 - 01:42 pm: |
|
Before you go tearing into that engine, check the linkage that connects the two throttle butterflies between the two carburetors.
If that linkage is set so that one butterfly is slightly open with the other one closed, the rpms will do weird things...... your problem being one of them.
That linklage must absolutely be set so that the butterflies open and shut at the same time, and at a idle..... both being shut completely. |
Elisha Danzig
Member
Username: zmasterflex
Post Number: 8
Registered: 04-2008
| | Posted on Thursday, May 08, 2008 - 01:51 pm: |
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If you buy a repair manual they explain how to do these types of things such as clean, repair, reset or replace reeds (and what to use). These manuals are written for people like you and me so they are understandable. Paper ones start at 30$, and CD ones are much cheaper. (I've got one on a CD, it's got a few hundred pages, I can print out diagrams whenever I want, and I have it installed on multiple computers). You can get them on eBay for very cheap. Good Luck!! |
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