1955 Johnson 5.5
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- This topic has 9 replies, 6 voices, and was last updated 2 years, 9 months ago by james hobson.
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June 6, 2021 at 5:01 pm #239610
Ok my 5.5 is only running at haft throttle when turned all the way to full no missing runs and idle is good just will not run wide open, high speed set smooth , carb was rebuilt I rechecked float level all good new coils and points compression is 85 and 90 new plugs gap set at 30 tho , the only thing that does not look right to me is time if plate only moves 3/4 to the end of plate looks like it could or should move close to the end to open carb all the way up carb has about 1/2 inch more throttle to be wide open will try to send pic any help would be appreciated.
- This topic was modified 2 years, 9 months ago by Mumbles.
June 6, 2021 at 5:16 pm #239612Yup, think you are correct… Did you have the throttle/twist grip pieces apart? If so, did the gears get “mis indexed”? Does the mag plate move freely? Try removing the clip that secures the mag plate to the vertical throttle rod to move it manually to ensure it is not jamming. There is a pin that fits through the bottom of the vertical throttle rod, that secures the vertical rod to the bottom throttle gear, perhaps the “ears” have sheared off.
Finally, make sure that the vertical throttle rod has not become twisted, this usually only occurs when something is binding in the system. In any event, the mag plate is not moving to its fully advance position and the carb is not opening up all the way.June 6, 2021 at 5:38 pm #239615Some mag cams are adjustable. There are 3 machine screws holding the cam to the mag plate — some cams have oblong holes for those machine screws — moving the cam away from the plate will engage the throttle sooner and have it open wider.
Make sure there isn’t a deep groove cut in the cam follower.
June 6, 2021 at 6:14 pm #239616Something has been changed on that motor. Magplate? Cam? Carburetor? That motor did not originally have a cam roller, just a metal rod. You can see the wear where it vibrated against the cam at WOT.
June 6, 2021 at 6:46 pm #239619The rubber hose on the carb rod was my idea to hold carb open more going to remove don’t think carb or cam or plate was ever changed
June 7, 2021 at 1:08 am #239634Your motor has the old style stamped gears, #’s 8 and 16, which can be bent or worn. Twisting the throttle with the tiller in the up position can damage them. If they are damaged, ’56 and later cast style gears and shafts will drop right in. As mentioned, gears 21 and 23 can be one tooth out of time which will prevent the mag from advancing fully Your vertical throttle shaft, #28, doesn’t have a plastic pin to break at the bottom but instead it is cast and has an ant rattle spring.
For the mag and carb to be that much retarded, I’d suspect the gear timing first.
June 7, 2021 at 4:20 am #239639OK, my money is on gears 21 & 23 out of time
June 7, 2021 at 10:44 am #239648Or the bottom of the vertical throttle shaft and the slot in gear 21 are worn.
June 7, 2021 at 1:10 pm #239655you need to find out what stopping it from turning open, also the rubber add-on is most likely going to mess with fuel/timing
June 7, 2021 at 1:26 pm #239656Ok guys I believe I found the open throttle problem looks like I had a missing screw on the mag arm my mess up thanks for all your help that help lead me to the problem and in the process I learned new info from your help again thanks.
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