I’ve always liked the look of the old Hill Climbing bikes. Big aggressive tires and huge sprockets for the low down gearing. Before I got into gasification or at least building them I have made a few motorized bicycles. My personal best is 46mph with a Harbor Freight 79cc engine that could still climb the steep hills here. Just one speed with a centrifugal clutch.
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My curiosity is peaked…
What did you build?
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I got it from a guy that races go karts, it has a billet flywheel with a built in 20 degree timing advance and a conservatively shaved head, and one of those multi pronged Autolite spark plugs. Even with premium gasoline it’s a bear to start up. Comes as those “Box Stock” kits. But with the billet flywheel I can rev it to maybe 9000 RPM without worrying about it grenading like the cast aluminim flywheels. I haven’t checked the valve clearance or upgraded the springs so I assume the valves will float before I reach the real top end, probably 6000 RPM with stock valve springs. Haven’t put it on anything yet.
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I don’t want to be sitting on top of any flywheel spinnng 9000 rpm. Anyway to make a scatter shield for that thing? Not a brainiac but I was always smart enough to use lock-tite and be real anal about torque specs when installing a flywheel.
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It has a pretty heavy cover, and I torqued down the flywheel nut myself. I’m probably going to build a plate to rest my leg on if I make it a Board Track Racer.
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I have some sugestions for anyone building a clone to run on woodgas.
Number 1:
Find a 14cc head off a Chinese 5.5 hp GX160 engine or a real Honda Head.
I like the Chinese one because they are all 14cc and the current head is 18cc.
If you decide to use the 18cc because you had q free one look for the Z4M piston from the GX160 that the 5.5 uses with the current 18cc head. This combination of parts will get you to 10:1 compression. You do not need heavier springs ( BTW if you building a gasoline race engine you want to use the G-200 valves springs from the old flat head 5 Hp they still sell them at the Honda dealer )
You gain nothing from billet parts here except maybe the ARC billet rod that has a really nice babbit bearing in and a hollow dipper form better oiling.
You absolutely MUST set your timing.
You ABSOLUTELY MUST use a timing light and start at 25 BTDC. I know this will pull start and I know its an improvement over stock and a good starting point
More to follow later
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I’ve never changed the timing on these little engines. I’ll be real interested if knowing how you do it.
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I already know from previous experience a real Honda GX160 has 25 deg timing and a GX200 has 20. So if you just swap the flywheel from a donor clone you have a bolt on solution…
Since you have the head off for a swap we can identify 0 TDC…
Timing a Small engine:
We need to make a piston stop of some sort that sticks down into the cylinder and bolts firmly in place a piece of flat bar steel with a bolt in the centre will do.
We will turn the flywheel back and forth and mark the stop both directions on the flywheel. The centre of this line is TOP DEAD CENTRE…
Next we need to mark in graduations the degrees up to lets say 35 deg. We measure the diameter of the flywheel and divide by 360 then we know how many inches or cm or mm we are using and we can mark it out on the flywheel…
Next we need to assemble the engine and run it and hit it with a timing light and a pointer to find out what we have for real stock timing.
Once we see where the timing is and how many deg it is we can calculate the amount of advance we want. Again we need that piston stop and we need to see the zero point and again we need to know how many inches we marked and then mark the flywheel where we want it on that piston stop. Pop off the flwheel and remove the key.
Lap the flywheel and we are going to run without a key form now on ( this is not an issue of you lap and assemble clean and dry. Trust me a properly torqued lapped flywheel will not move ).
The we reassemble and check with the timing light again to see how many real actual deg we have advanced the timing. From here on timing will be altered as needed by listening and reading the plugs. Wood gas creates a whole lot of new issues in plug reading. I have no idea how to read a plug on this fuel so its likely just a case of try and test to see what runs best. It would not hurt to monitor fuel consumption and use that as a means to an end for tuning.
I think between 25 and 30 is probably the range that will run best and be easiest to pull start more than that might cause more trouble.
Here is another more convoluted way to do it.
Here is a demonstration of a timing light on a clone drive end pulley instead of a flywheel. You can use a drive pulley to verify timing too ( in this case you see the grub screw )
Autolite AR 3910x ???
I have used them and they really i don’t see an advantage here. Its a good way around the tech man because its a surface gap plug that fills some combustion chamber volume.
I prefer the NGK BP6ES, remove the resistor button on the spark plug boot if you like it may let a little hotter spark if needed. You can trim and file the plug back 1/2 across the centre electrode if you like, Index it if you like and gap it to what ever you like…
All this is experimentation, but if you find you have a miss on wood gas try and close up the gap and see if that helps, then try the other stuff.
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I have a inverter generator that uses a clone gx390 engine ,and as i am no expert on these small engines i wonder if there are any mods that i can apply to try squeeze some more power out of this stock engine .
I have worked on this brand and model of this generator a few times over the past 5 years and so i know how hard it will be to do much without having to take out all the electronics of the inverter and wiring to even get at the coil , but in my head maybe moving the coil would be a simple way of helping to advance the ignition and your mention of using the smaller cc clone head would you know what head i would have to look for that would fit my model engine .
Really have no experience of even stripping or rebuilding these engines so any advice would be great .
Dave
I have a 390 I need to strip the head off…
I have a 301 clone with large valves…
I think the 301 head might be a good modification for the 390 but it depends on flow.
Other than that it may not be feasible to do anything to it other than an ignition upgrade to the IGX CDI and some timing.
There is a 440 clone that may share a crank with the 390. Do you want to build an engine? Its up to you and some reading and research on my part before I give you anything further advice on the 440.
It would appear the 420 Predator and the GX390 share a crank…
This head is a bolt on but is it the same as the one I have?
A better than stock rod for longer life.
That 301 inline valve clone head I have is very hard to find. The one I have is off a Huskvarn snow blower.
Anything can be done friend.
But how much trouble is it worth?
Going to add before the thread is split and moved.
Try not to make a change you cannot un-do.
bolt on parts and second block if its cheap are not a big deal, you can always go back to stock if you are unhappy with what you built. Woodgas specific Honda engines are a new idea and clone parts make all kinds of experimentation possible.
We might read the topic above, and move our discussion to the correct topic title for small engines for gasification. We have strayed off a bit.
Bob
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Good point Rob off topic
Apparently I can do this somehow with my new privileges.
I have no idea how to, so if you got it, and get it could you split the thread?
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Hi @Chris could you split this thread and make new topic. This is some great discussion and it needs it’s own topic.
Thanks you.
Bob
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while we wait for Chris to split this thread , if i can just say to Wallace that at this moment in time my gx390 engined generator is up and running and producing power so i wont strip it out while its all good , but as mentioned other than the head and carb and with a little coaxing the coil are the only parts of the engine i have access too while it is all in the frame in a running condition and so was just maybe seeing if i could move the coil to maybe a little before its standard trigger point to advance the engine a little rather than remove the flywheel and lap or key a advance and maybe skim the head a few thou to increase the compression , or bolt on head from another engine that would also increase compression .
I had look at a 301 head and it looks so different on the valve cover and would have no idea if it would fit at all , here in Australia we don’t have Predator engines just a bunch of no name clones
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Hi Chris Saenz:
I can not edit my 8th post, actualy the post number 13 of this topic.
Do you now what I am doing wrong?
B.R.
Eddy Ramos
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@Chris Eddy is having trouble editing his posts.
This is a better way to contact him Eddy by typing @Chris
Bob
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Thank’s Robert:
I have already wrote to Chris. I am waiting for his feedback.
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Hi Eddy, you should be able to now. By default very old posts are not editable. I unlocked that one for you.
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Since this is a theme for drawings of gasifiers, I will add my last variant, otherwise it does not belong to 100% charcoal gasifiers, but is 100% wood, but also contains a carbon gasifier in the lower part, construction of air-cooled vertical grille in the style of imbert. …
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I think we should dub it, “Charcoal Refinery On The Go”.
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