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WitsEnd
06-30-2018, 06:59 PM
I'm new to this machine and website, but not to small engines. I've had it running after religiously going thru the motions (gas, spark, compression). I had it purring like a kitten and riding great yesterday, today it's dead. I checked the coil, spark is strong, shot sarting fluid in the cylinder and not even a bark. Compression was only 60psi. I will personally paint your house if you can tell me what I'm missing!!! It's 100 degrees today in Michigan so maybe I'm just dehydrated!

ironchop
06-30-2018, 11:18 PM
So you parked it after riding it and it ran great until then but now it won't start and suddenly lost compression?

No issues, smoking, backfiring, or loss of power while it was running?

Have you checked to see if the head gasket is blown or if the head is still torqued correctly?

Does it have a compression release on the head that might have gotten stuck?

Need more info



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WitsEnd
07-01-2018, 08:01 PM
Hello IronChop, thank yo so much for responding! I don't want to take up your time so here are the bullet points...

-No backfire, loss of power, tranny smooth
-No oil leaks around head or anywhere
-Removed compression release cable but took exhaust valve cover off and made sure nothing is stuck
-Didn't torque head for lack of tech manual but did lash valves and checked valve train timing, etc

This thing rides strong, idles down nice, doesn't sputter upon acceleration

I just can't get it to start now...ruled out vapor lock, etc

It's a nice trike but I don't want to waste too much time on it due to it's age and lack of parts availability and tech docs.

I appreciate you...God Bless and have a great holiday!!!! -Darren

Rob Canadian
07-01-2018, 08:29 PM
Hey Darren. Welcome to the site. Don't worry about taking up our time. That is what we are all here for.

I am not familiar with your machine. When did you remove the compression release cable? Before or after you had this issue. Trying to get a time line on what you did and when. As Ironchop asked. Ran 1 day fine and not the next?

WitsEnd
07-01-2018, 08:57 PM
Hi Rob, appreciate the kind words! Decompression cable removed before I had issues. I left the lever on the exhaust valve cover so future riders could pull rope to compression stroke and lift lever manually for an easier pull. I had a vapor lock on carb at one point but have since set the float, cleaned the carb, etc. (had gas in the air box) I did the couple drops of 40 weight down the cylinder and compression went up to 90 lbs but still wouldn't even bark with starting fluid in the combustion chamber. Plug is always dry...should I unhook the airbox from the carb intake....maybe unhook the exhaust? I really haven't altered anything and it runs/rides so nice once I get it started. Thank you, God Bless!

Rob Canadian
07-05-2018, 06:06 PM
Did you get anywhere with this?

I have never had a Yamaha. Not sure how the decompression system works on yours. I know on some models people tie strap the lever into a certain position.

WitsEnd
07-05-2018, 06:51 PM
Thanks for checking back...I finally got it running and starting great. I'm not sure if I need a larger pilot jet, but compression comes up to 152 psi when I hold throttle in about 30% of travel. Problem is I have to hold throttle with one hand and pull the rope with the other....AWKWARD!!!! Perhaps originally there was a mechanism to hold throttle lever partially open.Again, I have no way of knowing without any literature and this trike is the first I've put my hands on...I'm just a motor man as a hobby. I sure do appreciate you and maybe this thread will help others!! Be well, ride safe, and God Bless!!!

ironchop
07-05-2018, 07:03 PM
Thanks for checking back...I finally got it running and starting great. I'm not sure if I need a larger pilot jet, but compression comes up to 152 psi when I hold throttle in about 30% of travel. Problem is I have to hold throttle with one hand and pull the rope with the other....AWKWARD!!!! Perhaps originally there was a mechanism to hold throttle lever partially open.Again, I have no way of knowing without any literature and this trike is the first I've put my hands on...I'm just a motor man as a hobby. I sure do appreciate you and maybe this thread will help others!! Be well, ride safe, and God Bless!!!You should hold the throttle wide open and pull rope three or four times to get the correct compression reading.

Leaving the throttle closed means your intake can't "gulp" enough air in to compress a sufficient volume

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Rob Canadian
07-05-2018, 07:44 PM
You should hold the throttle wide open and pull rope three or four times to get the correct compression reading.

Leaving the throttle closed means your intake can't "gulp" enough air in to compress a sufficient volume

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Well said. Yup the engine is just a air pump. Most people spray starter fluid into the intake. A quick spray down the camber may not do it. By the time you put the plug back in. It is a lost cause.

ironchop
07-05-2018, 08:21 PM
BTW...Here....free three-wheeler manual downloads in case you need it in the future

https://threewheelermanuals.com

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WitsEnd
07-05-2018, 10:59 PM
I can't thank you both enough!! I understand the "air pump" analogy for sure, I'm just not familiar with throttle body slide carbs and the internal circuits. Should there be a cold start "position stop" on the throttle? Thanks for the manuals link as well Ironchop!