78 HD Engine rebuild complete, Governor removed, Is there a rev limiter?

Boliver · 08-23-2011, 12:26 PM

Hi
I just got done with a complete engine rebuild on my 78 HD cart. The governor parts were long gone before I got the cart. My question is: How do I keep the engine from over revving? The manual references top speed at 3000 rpm. Is there a way to set max RPM without the parts for the governor? I really don't want this thing to blow up (again).
Thanks in advance!

Lochlin · 08-23-2011, 06:14 PM

It seems as if the above post answers it all but if you are still concerned did you look into adjusting your throttle cable to see if you can adjust it back? Some after market cables have adjusting nuts on them (mine does, at the carb) but I am not sure if orginal one's did.

Whitespider · 08-23-2011, 06:32 PM

The 3000 RPM was the factory setting, the governor could be field adjusted a bit higher than that. The reason for the governor was to keep cart speed "safe" and constant when going up hills and such (i.e. at the 3000 RPM setting the governor still had plenty throttle left if needed to keep cart speed constant). I believe the 3000 RPM setting was equivalent to an approximate 10 MPH, and field adjustable to approximately 15 MPH. The governor was not intended as a rev limiter... it was used to limit throttle travel so some would be left if needed, and to keep the cart at a safe and constant speed.

As to "over-revving" the engine... I really don't think you could, the carburetor just ain't big enough to deliver enough fuel/air mixture to get engine speed much past 6000 RPM's, and that's with the rear wheels off the ground. The RPM's are not your enemy, near any 2-cycle engine should handle 8000+ RPM's with no issue, if it's tuned properly (some run as high as 15,000 RPM). But a fuel mixture set too lean is your enemy at any RPM, it will burn down a piston in short order. It is the air/fuel/oil flowing into the crankcase and up through the cylinder that keeps the engine lubricated and cooled...

Make absolutely sure the air/fuel mixture is set correctly (just a bit richer than what the book says because RPM will be a bit higher at full throttle). The Tilotson carb used on the Harley carts does not have a "high" speed adjustment screw, but the "low" speed screw does impact the "high" speed fuel mixture, set it as rich as you can without affecting run/acceleration quality. Use a good quality 2-cycle oil and mix the first tankful "rich" (say 40:1) so the cylinder and rings get plenty of lube while they seat (do not use a synthetic 2-cycle oil during break-in!).

After break-in and when you go to your standard fuel/oil mix be sure and readjust the carb. Personally I don't trust the recommended 85:1 fuel/oil mix for off the golf course, govern-less use... I'm using a 65:1 mix without issue... Makes the carb adjustment just a bit less critical.

Lochlin · 08-23-2011, 06:41 PM

Sorry about the double post. I can't figure out how to delete a post.

It seems as if the above post answers it all but if you are still concerned did you look into adjusting your throttle cable to see if you can adjust it back? Some after market cables have adjusting nuts on them (mine does, at the carb) but I am not sure if orginal one's did.

Boliver · 08-24-2011, 08:37 AM

Thanks for the useful info Whitespider. I was paranoid about over rev so I went back to the box of old parts and found the gov bracket and spring (no shaft). I fabbed up a shaft out of a piece of brazing rod and set the gov to kick in at about 3800 RPMs (slow). I also riched up the carb to about 1.2 turns open on the mixture screw. The mix I had in was already oily. The old girl seems to be running quite well.

My plan is to run with the gov for the first tank or two and then either back it off or take it back off all together.

Thanks again

Boliver · 08-30-2011, 06:34 AM

The cart is running good but a bit smokey from the rich mix and tuning. Smokes out anyone on the back (would probably fume anyone on the back even if it wasn't smokey). Does anyone have a suggestion for exhaust management? I have some hi temp silicon tubing that I was considering using to get the exhaust to the side/rear of the car. I did a little research and learned that high back pressure can cause the piston to over heat so I want to be sure that doesn't happen (again). It has the stock muffler on now with a 3 inch long pipe sticking straight down towards the ground. I would prefer to pipe the exhaust out the rear drivers side corner.
I guess my questions are:
Are there any exhaust pipe diameter/length combinations that will not create too much back pressure?
What is the best type of pipe/hose to use and where to get it?
Thanks!

Don B. · 09-09-2011, 12:08 AM

I run the same 50:1 mix I use in my Echo and Stihl 2 cycle stuff, and have very little smoke.

ScooterMcTavish · 09-09-2011, 04:28 PM

Could need a muffler BBQ.

My EZGo had sat for some time, and was run too rich before I bought it, manifested through back pressure issues and a cloud of blue smoke (caused by the muffler heating up).

Trust me, it really does work!

http://www.buggiesgonewild.com/gas-y...-hot-pics.html

08-23-2011, 12:26 PM	#1
Boliver Not Yet Wild Join Date: Aug 2011 Posts: 16	78 HD Engine rebuild complete, Governor removed, Is there a rev limiter? Hi I just got done with a complete engine rebuild on my 78 HD cart. The governor parts were long gone before I got the cart. My question is: How do I keep the engine from over revving? The manual references top speed at 3000 rpm. Is there a way to set max RPM without the parts for the governor? I really don't want this thing to blow up (again). Thanks in advance!
Boliver Not Yet Wild Join Date: Aug 2011 Posts: 16

08-23-2011, 06:14 PM	#2
Lochlin Gone Wild Join Date: May 2011 Location: Pittsburgh Posts: 2,953	Re: 78 HD Engine rebuild complete, Governor removed, Is there a rev limiter? It seems as if the above post answers it all but if you are still concerned did you look into adjusting your throttle cable to see if you can adjust it back? Some after market cables have adjusting nuts on them (mine does, at the carb) but I am not sure if orginal one's did.

08-23-2011, 06:32 PM	#3
Whitespider Getting Wild Join Date: Mar 2011 Location: NE Iowa Posts: 117	Re: 78 HD Engine rebuild complete, Governor removed, Is there a rev limiter? The 3000 RPM was the factory setting, the governor could be field adjusted a bit higher than that. The reason for the governor was to keep cart speed "safe" and constant when going up hills and such (i.e. at the 3000 RPM setting the governor still had plenty throttle left if needed to keep cart speed constant). I believe the 3000 RPM setting was equivalent to an approximate 10 MPH, and field adjustable to approximately 15 MPH. The governor was not intended as a rev limiter... it was used to limit throttle travel so some would be left if needed, and to keep the cart at a safe and constant speed. As to "over-revving" the engine... I really don't think you could, the carburetor just ain't big enough to deliver enough fuel/air mixture to get engine speed much past 6000 RPM's, and that's with the rear wheels off the ground. The RPM's are not your enemy, near any 2-cycle engine should handle 8000+ RPM's with no issue, if it's tuned properly (some run as high as 15,000 RPM). But a fuel mixture set too lean is your enemy at any RPM, it will burn down a piston in short order. It is the air/fuel/oil flowing into the crankcase and up through the cylinder that keeps the engine lubricated and cooled... Make absolutely sure the air/fuel mixture is set correctly (just a bit richer than what the book says because RPM will be a bit higher at full throttle). The Tilotson carb used on the Harley carts does not have a "high" speed adjustment screw, but the "low" speed screw does impact the "high" speed fuel mixture, set it as rich as you can without affecting run/acceleration quality. Use a good quality 2-cycle oil and mix the first tankful "rich" (say 40:1) so the cylinder and rings get plenty of lube while they seat (do not use a synthetic 2-cycle oil during break-in!). After break-in and when you go to your standard fuel/oil mix be sure and readjust the carb. Personally I don't trust the recommended 85:1 fuel/oil mix for off the golf course, govern-less use... I'm using a 65:1 mix without issue... Makes the carb adjustment just a bit less critical.

08-23-2011, 06:41 PM	#4
Lochlin Gone Wild Join Date: May 2011 Location: Pittsburgh Posts: 2,953	Re: 78 HD Engine rebuild complete, Governor removed, Is there a rev limiter? Sorry about the double post. I can't figure out how to delete a post. It seems as if the above post answers it all but if you are still concerned did you look into adjusting your throttle cable to see if you can adjust it back? Some after market cables have adjusting nuts on them (mine does, at the carb) but I am not sure if orginal one's did.

08-24-2011, 08:37 AM	#5
Boliver Not Yet Wild Join Date: Aug 2011 Posts: 16	Re: 78 HD Engine rebuild complete, Governor removed, Is there a rev limiter? Thanks for the useful info Whitespider. I was paranoid about over rev so I went back to the box of old parts and found the gov bracket and spring (no shaft). I fabbed up a shaft out of a piece of brazing rod and set the gov to kick in at about 3800 RPMs (slow). I also riched up the carb to about 1.2 turns open on the mixture screw. The mix I had in was already oily. The old girl seems to be running quite well. My plan is to run with the gov for the first tank or two and then either back it off or take it back off all together. Thanks again
Boliver Not Yet Wild Join Date: Aug 2011 Posts: 16

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08-30-2011, 06:34 AM	#6
Boliver Not Yet Wild Join Date: Aug 2011 Posts: 16	Re: 78 HD Engine rebuild complete, Looking to manage exhaust The cart is running good but a bit smokey from the rich mix and tuning. Smokes out anyone on the back (would probably fume anyone on the back even if it wasn't smokey). Does anyone have a suggestion for exhaust management? I have some hi temp silicon tubing that I was considering using to get the exhaust to the side/rear of the car. I did a little research and learned that high back pressure can cause the piston to over heat so I want to be sure that doesn't happen (again). It has the stock muffler on now with a 3 inch long pipe sticking straight down towards the ground. I would prefer to pipe the exhaust out the rear drivers side corner. I guess my questions are: Are there any exhaust pipe diameter/length combinations that will not create too much back pressure? What is the best type of pipe/hose to use and where to get it? Thanks!
Boliver Not Yet Wild Join Date: Aug 2011 Posts: 16

09-09-2011, 12:08 AM	#7
Don B. Gone Wild Join Date: May 2011 Posts: 156	Re: 78 HD Engine rebuild complete, Governor removed, Is there a rev limiter? I run the same 50:1 mix I use in my Echo and Stihl 2 cycle stuff, and have very little smoke.
Don B. Gone Wild Join Date: May 2011 Posts: 156

09-09-2011, 04:28 PM	#8
ScooterMcTavish Gone Wild Join Date: Oct 2009 Location: Manitoba, Canada Posts: 363	Re: 78 HD Engine rebuild complete, Governor removed, Is there a rev limiter? Could need a muffler BBQ. My EZGo had sat for some time, and was run too rich before I bought it, manifested through back pressure issues and a cloud of blue smoke (caused by the muffler heating up). Trust me, it really does work! http://www.buggiesgonewild.com/gas-y...-hot-pics.html

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