foamcut

My Feedback: (40)

Has anyone converted a four stroke trimmer to gas / glow (2/3 gas mixed with 1/3 10% glow fuel)?
I just picked up a 26cc 4 stroke trimmer head and I'm interested in any tips before I tear into it.

Thanks

captinjohn

It should work as long as you keep the Glow driver on at low RPM settings. Put a glow plug adaper and 4 cycle plug in it and fire it up!!! Capt,n

davewallace

My Feedback: (29)

foamcut,
The hard part will be making a glow plug adapter the the Ryobi 26cc. It usea a special thread plug and it is very deep. The plug thread measures 10mm diameter and is 10mm deep. No one makes an adapter, so you are on your own. You also may have trouble getting enough fuel, since the main jet is fixed. The four stroke pumper carbs use a modified pump action, due to the weak pulse available.

Dave

foamcut

My Feedback: (40)

Dave,

Great input...thanks. It sounds like I'm going to need to fabricate the necessary parts and modify or replace the carb.

davewallace

My Feedback: (29)

foamCut,
I measured the bore of the plug while still in the package. It is slightly over 1/4". A glow plug is 1/4x32 thread, so it is a little large to tap for a plug. you will have to fabricate a new adapter. The threads should be about 5mm deep and the plug recessed into the body as much as possible. A rim at the top could be slotted to allow a large screw driver to tighten the adapter. I thought about doing this, but the carb mods and plug issues stopped me. Someone in an earlier thread drilled out the main jet in the stock carb. You could do a search and find the thread. If you make a good adapter, make an extra for me. This would save a pound. Mine weighs 76oz with mag. ooch!

Regards, Dave

foamcut

My Feedback: (40)

Dave,

The 10mm hole you mentioned would convert to .3937". If a standard glowplug has a 1/4 X 32 thread this would only leave 0.1437" worth of material for threads. This is a pretty narrow margin as you indicated.

I just ordered my engine so I don't have it here to examine the inside of the combustion chamber. Does it look like there's enough room in the head to drill and tap for a standard 14mm spark plug (adapter)? If not I may have to devise a way to modify a glow plug to fit the 10mm hole (ie braze the threads and recut the threads). I guess another alternative would be to weld the current spark plug hole in the head closed and then drill / tap for the 1/4 X 32 glow plug.

Let me know what your opinion is. The weight of the four cycle will definitely benefit from the elimination of the coil and mag.

Hmmmm this discussion of modifications to the glow adapter makes think that a Lanova chamber conversion would be a good alternative for the diesel lovers out there....wonder if anyone has already done it.

captinjohn

I have a 4 cycle twin ( Kavan 50) that I have run on Glow fuel and it seems to up the level(possibly from piston blow by) in the crankcase, which has a dip stick. With higher contents of oil in glow fuel...you may not need much or not even any oil in crankcase? I do not know this...never had a Ryobi 4 stroke running on glow. Best Regards Capt,n

davewallace

My Feedback: (29)

Foamcutter,
I would make a screw in adapter. Here is a picture of the plug. The hole in the middle is about 1/4". The valve train and cover take up most of the head.

Dave

foamcut

My Feedback: (40)

Dave,

Thanks for that picture. I'm still working on the concept.

I wonder if the spark plug can be gutted and then modified to accept a glow plug in the area where the electrodes would normally be...



Capn' John,

You're thinking just like I am. I'm also going to pursue this with the intention of eliminating the need for the crankcase oil.

av8tor1977

My Feedback: (6)

The problem is that the feeling has been the glow plug should be down at the end of the threaded part of the spark plug shell, both to increase compression and to expose the glow plug to the mixture in the best fashion. When doing this with a standard spark plug shell when making a homemade adapter, the plug shell gets really thin at the thread area in order to provide an entry for even a narrowed down glow plug socket or wrench. With the plug shown, it's going to be a real problem it looks like....

Another thought is that we are using a four stroke glow plug in our two strokes to keep the plug hot enough with our gasoline/glow fuel mixture. A four stroke might be problematic in that area as the glow plug may cool off too much in between power strokes. As mentioned, you may need glow power on at low throttle, or you may need to increase the methanol and/or nitro in the fuel mix.

AV8TOR

foamcut

My Feedback: (40)

av8tor,

Thanks for that feedback. i'm beginning to think that welding the spark plug hole shut and then drilling, countersinking, and tapping for the 1/4 X 32 glow plug might be the best way to pursue this.

Do you know if anybody tried the Glowbee style plugs in a gas / glow application?


After reading the 43 page thread on gas / glow (best 4 hours I've spent on a research project) I've concluded that I will run some kind of glow plug heat (either constant or variable). I'm expecting the methanol to be the ignition mechanism rather than the primary power source in the fuel. I am really looking forward to benefits of the hybrid fuel / ignition conversion. I've been wanting to pursue conversions for some time now but have been stymied by the ignition issue. Now there is an alternative to gas / spark ignitions without incurring the "methanol only" issues.

davewallace

My Feedback: (29)

As I said above, the hole measured 1/4" which is a little large for a 1/4"x32 tap. Maybe the hole could be silver soldered and then tapped. The threaded section could be cut down to expose the hot coil more. Maybe the head could be welded shut and drilled and tapped.

Dave

captinjohn

How about the right size Heli-coil. Drill for Helicoil and then install the Helicoil for same size as standard glow plug. NO 2 Method: If you remove head...can you just Heli-arc the spark plug hole shut...dress-up weld in dome and drill , tap and spot face for glow plug. If that is not possible I have one more idea. Leave spark plug in and drill from inside the cumbustion chamber to a new spot where you can spot-face and tap for a glow plug in different location. Best Regards Capt,n

foamcut

My Feedback: (40)

Capn' John,

These all sound like great and very creative ideas! Once I get the engine and get it disassembled I'll determine which is the most practical.

aero nut

In the gas fuel glowplug no ignition thread I read about one of our members converting a Robin 26 CC four stroke into gas/glow without methanol but keeping it hot at all times with the battery on I will try to find the page that it was on.
Found it: page 8 contributor is gsmith6879

foamcut

My Feedback: (40)

Aeronut,

Thanks for that feedback. I'll try to contact gsmith to see if he can shed some new light on the issue.

Diesel_Flyer

Anybody need an extra Ryobi 26cc ? I've got one already converted I'm not going to use.

captinjohn

foancut: How is the 4 cycle on gas/glow going. I have been busy redoing the Bathroom. New everything in that room, when done!!!! Capt,

foamcut

My Feedback: (40)

CapnJohn,

My engines haven't arrived yet. I have 4 on order. In the meantime I've been researching everything I can find on 4 stroke conversions here on RCU. I've seen some pretty creative engine mounting designs and read a lot about carb problems. Some of that research should pay off as preparation for the conversion process. One example of that info is the evolution of the oiling system in the Ryobi 26cc 4 strokers. Apparently early models had problems with the crankcase venting and would spit oil when inverted. Later generations seem to have fixed this problem and appear to operate inverted without a problem. The engines I have on order are knock offs so I don't yet know which of these issues will need to be overcome....I just know that tinkering with engines is my favorite part of this hobby.

I'm going to prepare a pictorial review of the process as the conversion process evolves.

captinjohn

foamcut: I was wondering how the 4 cycle project was coming? I have another guy that would like to learn more about the 29cc Ryobi four stroke. What is the tube for that goes to the breather? Is it a crankcase ventilator? Thanks Capt,n

Iflyglow

My Feedback: (79)

Why not just purchase an adapter. B&B specalties should have them, along with any source that sells giant scale raceing engines. Most all of them are run on glow. Horizon was selling a G23 glow a few years ago.

Iflyglow

My Feedback: (79)

Why not just purchase an adapter. B&B specalties should have them, along with any source that sells giant scale raceing engines. Most all of them are run on glow. Horizon was selling a G23 glow a few years ago.