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Discussion Starter · #1 ·
I had a lot of trouble with the Briggs engine in my XUV 550. It was incredibly sensitive to a slightly dirty air filter and loved to fowl plugs. Deere's response has been that the vehicle should not be allowed to idle for more than 30 seconds and to not use it for short trips. Go figure a Gator that should not be used for landscape maintenance that involves short trips and idling... So at 100.3 hours out came the engine.

I replaced the Briggs & Stratton engine with a Honda GX630. The Deere spec'd Briggs has a non standard taper on the crank shaft and in the drive clutch. I had the option of taking apart a brand new engine to replace the crank and keep the stock clutch or to replace the clutch as well. In order to stay with a stock engine and clutch I replaced both with ones having a 1" straight shaft.

The Honda is very similar in overall size to the Briggs but has a more boxy shape. At this point I'm still confident it will be a quick and easy engine swap.



The first problem I encountered is the engine mounting base which is formed of sheet metal in a "U" shape. The Gator had a semi circular cutout for the flywheel and fan shroud of the Briggs but the larger and boxier Honda hit so I had to do some trimming of the vertical flange.

 

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Discussion Starter · #2 ·
I was really, really hoping I would get lucky with the exhaust but... no! The center to center bolt spacing for the exhausts is wider on the Honda. Luckily there was enough metal on the flanges to elongate the holes.



Also, the axis of the exhaust mounting studs is about 5 degrees different and the spacing between the two cylinders is slightly greater so out came the saw and welder. It's a pretty complex exhaust for a simple little vehicle. Beside simply connecting the engine to the muffler I wanted to retain the stock heat shield, clear clutch housing's aluminum casting and miss the choke & throttle linkages. Needless to say everything is in very close proximity as this is a very "busy" area.





While I had them off I gave the inlet area of the pipes a quick polish. With the sharp bends I did not think there was much to gain but there were some pretty large weld blobs in the flow path of the factory pipes.
 

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Discussion Starter · #3 ·
Since my new engine and clutch bore are 1" straight with a key there is nothing to establish the clutch's position on the shaft. I attached the driven clutch to the transmission and using a long straight edge and scale (ruler) established a rough position for the drive shaft. The crank of the engine has a nice, broad flange for a spacer to bear upon. My dad helped out and took some 1 1/2" diameter aluminum and bored and reamed it .002" over the engine's shaft diameter.



The spacer can be made shorter but I don't have a way of making it longer short of starting over so it's what I think is about .050" long which in the end turned out to be perfect.

 

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Discussion Starter · #4 ·
The problems continued. Even though the overall dimensions of the Honda are very similar to the Briggs it's more squared shape caused problems. The bracket and linkage that controls the four wheel drive and differential lock were a real pain. To keep the linkage pull lines in order I had to modify the four wheel drive control lever moving the actuator point up 1 1/4" higher.

First was modifying the 4wd control lever. It sounded easy when I came up with the idea. I welded up a piece to move the attach point for the actuating spring. This structure raises the spring attach point and adds strength to make up for what I cut away from the stock arm. The problems started when I put the stock, cast arm on the band saw and only made a scraping sound and left nothing but a little shiny spot. Out came the cut off wheel and 20 minutes of sparks later the offending part was removed. I placed my already made steel assembly on top and tried welding... bubble, bubble, fizz. I stopped welding and I flipped the helmet up to see the weld bead on fire. Not normal. The weld was crap with no penetration into the Deere cast arm. I ended up having to take it to a weld shop where they stick welded it with nickel. I hope it holds.

Next I modified the stock bracket holds the cable end for actuating the 4WD and differential lock. I cut out an arc where it was hitting the engine and bent it so the cable attach point was elevated by 3". Unfortunately the cutting to clear the engine removed the flange or lip that was bent down on the side and stiffened the bracket. So I had to bend and form steel to add a stiffening lip to the bracket.





Unfortunately I was in a very, very bad mood working on the cast 4WD actuating arm and did not take photos during fabrication. The weldment I added and that was nickel welded is where the spring attaches.

 

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Discussion Starter · #5 ·
Hooking up the throttle was pretty straightforward. Trimming the big plastic end of the Deere throttle cable allowed it to be gripped by the Honda's cable clamp. I'm not crazy about the throttle and choke linkages so close to the exhaust pipes but there is not much I can do if I want to preserve the engine's governor. If it poses a problem my plan B will be to run without the mechanical governor. The engine will still be protected by it's electronic ignition limiter which kicks in at 4'250 rpm.

The engine's choke cable attachment put the cable dangerously close to the exhaust. There was an unused tapped hole on top of the engine's linkages plate so I made a bracket to hold the choke cable. It looks complex but was one of the easiest builds for the day.





I re-attached the clutch housing base casting and bottom plastic. The driven clutch is in place and I have the drive clutch on there which required a long 3/8-24 grade 8 bolt. A bit of an oddball at 5 1/2" long so I had to wait for the brown truck to deliver the one bolt holding up the project.

I've also been working on the heat shielding around the exhaust pipes. Not much worthy of photos. The largest pieces work with slight trimming or moving bolt holes. I'll have to do some custom fabricating up forward where the header is right under the seat. I don't want to set my but on fire.
 

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Discussion Starter · #6 ·
Work on the exhaust heat shield around the front to protect the passenger compartment plastics was best done in place. I fabricated little steel bits to cover the open spots and a bracket to attach the shield to the forward part of the engine. The exact placement was much easier to do in place so I tacked everything while the shields were on the engine.

First step is to cover everything in leather. I'd feel like an idiot if I set the bloody thing on fire at this point.



To the right of the dipstick tube you can see some of the pieces I tacked in place. No fancy fitting or finishing at this point since they will be out of sight and I was running out of patience.

 

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Discussion Starter · #7 ·
Next came the wiring. I was mistaken when I thought there was a unused connector that did what I needed so I had to add a relay since the Briggs and Honda ignition are opposite. The Briggs engine runs and you ground the ignition wires to turn it off. The Honda needs the ignition wires grounded to run and the engine dies when the ground is lost.

I mounted the voltage regulator next to the winch solenoid and circuit breaker. It's a relatively protected location under the passenger seat about where you 850 guys have an engine. Just to the left of the voltage regulator are the controls for my front winch.



After hooking up the fuel line it's time for a test run. I did not want to risk starting it inside so I wheeled it out between thunderstorms. It looks rather funny without the body panels and bed. A bit more like a dune buggy.



 

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Discussion Starter · #8 ·


Notice something?

No air filter. At first I tried cutting the stock Honda plastic air filter housing and I was able to get the base piece in place but the filter was hitting the seat belt mounts. Cutting out the seat belts would have been relatively easy and allowed using the Honda air filter but... it would be unprotected against rain and water when washing down. The concave domed top of the filter cap would even funnel the water right into the carb so I'm going to make an adapter and run tubing up to the stock Deere air filter.

In the photo above the black plastic piece in the center is the carburetor intake so I decided to make a plate and adapt it to round to accept flex tubing and run up to the stock air filter.

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If you've ever wondered what the stock Briggs breathed through. It's this tiny 1" diameter intake.



Here is the adapter plate I made for the Honda carb sitting over the Briggs intake. HUGE difference in area.

 

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Discussion Starter · #9 ·
The inlet for the Honda engine is about 2 1/4" by 3 1/2" in a oblong crescent shape (could they make it any more difficult?). The round fitting on the Deere air filter housing is 2 1/2" diameter so I decided to run 2 1/2" tubing between the two. In order to make the transition I took a piece of 1" thick Delrin and after drilling the holes for mounting I used a 2" hole saw to remove the bulk of material from the center. Then I lightly scored the top side with a 2 1/2" circle. On the bottom side I marked out the shape of the Honda's inlet and went crazy with the die grinder with a coarse sanding bit.



There was a opening in the exhaust heat shielding facing the carburetor so I attached a separate shield to protect the plastic. This one is made from aluminum to help keep the weight down since it's supported by the plastic intake which in turn is supported by the carburetor. The round fitting on top is also aluminum and screwed in place with some caulk to insure an air tight seal.

 

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Discussion Starter · #10 ·
I used aircraft SCEET tubing to connect to the stock air filter. SCEET has a silicone layer inside and out so it offers a smoother air flow path and is very heat resistant.





And finally everything goes back together.

 

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Discussion Starter · #11 ·
The engine was working well (famous last words...). I put a GPS in and decided to see what my speeds were. I was cruising along at 25 mph a mile from home and I put my foot down... only to feel the pedal go limp and the engine dropped to idle. Sonofa $%#@ ! Walk home, get a tractor and tow it home.

During the build I had merely cut the end off the Deere throttle cable and put it into the fitting on the Honda which has a screw to clamp down on it. I knew it was not good to have a screw bearing down on a cable but I did it anyhow trying to save some time and avoid one more project. That last bit of throttle really fighting the governor was more than it could take and the cable partially broke and slipped.

The stock throttle cable has a .050" core which is seemed tiny so I made a new core using 1/16" (.062") cable and instead of relying on the throttle arm's little screw I crimped a ferrule to take the tension. It's been doing well so far, though I'm not putting my foot down when far from home.

The engine is similar to the Briggs in rpm so I was not expecting any increase in speed. I get about 25 mph at 3'600 rpm and the throttle advances easily up to that point. Above that I can really feel the governor fighting back. It's fine by me. It will spend most of it's life turning less than 3'000 rpm and the added resistance lets me know I'm getting into the overspeed realm. So far I've only had it up to 4'050 and it seems much happier than the Briggs engine.

I've got 1.7 hours on the engine mostly in test runs shaking out bugs. I can already notice a dramatic reduction in fuel consumption even with an engine much larger (580 versus 690cc). And power... WOW! What a dramatic difference. It will never be a speed demon but hill climbing with a load and acceleration are much improved and best of all. It will sit there idling happy as can be. Letting the Briggs idle for any period you could smell the gas and see the carbon building up on the muffler's exhaust. Not the Honda. It just sits there idling happily.

I'm not totally bashing the Briggs engine. It should have had better head gaskets from the beginning but Deere is taking care of that. Still not a good customer experience to be blowing head gaskets at less than 100 hours. Then there is the carburetor. I don't think they could have chosen a cheaper piece of crap and I think it's 75% of the problem with the Briggs engine in the 550. It might be ok for a application running at a fixed rpm and load but it's just a really simple, cheap carburetor not suitable for a vehicle application.
 

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Very impressive engineering. So i assume you are a mail carrier. LOL

So how did all the electrical connect up? Did you have to change any plug ins?
 

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Discussion Starter · #13 ·
The grounds and starter connections were the only ones that did not require modification and just hooked right up. The charging wires and fuel shutoff solenoid just required replacing connectors. Then things got more difficult as the Honda's ignition system is opposite the Briggs. The Briggs is turned off by grounding the ignition system while the Honda must have it's grounded in order to run and is open to turn it off so I had to use a relay to reverse the logic.

The biggest issue was that I lost the feature that prevents you from driving through the parking brake and the new engine has so much more low end power that you don't even feel the brake being engaged. I do not have a wiring diagram for the 550 so I just wired a loud beeper & bright blinking light on the dash that sounds whenever the ignition switch is on and the parking brake is set.



I really wanted to get the Gator out of the shop so I just took two wires from the parking brake switch to control my beeper. Unfortunately my hour meter no longer works. Temporarily I have a cheap electronic tach/hour meter hooked up but would like to eventually get the factory hour meter working again.
 

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So it is basically done Dane?
 

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Nice job Dane!
I love doing jobs outside of the box. You're work looks great.
I teach a Heavy Duty Mechanics program at a local University and we end up doing neat tasks like this as well.
We are now working on some Cummins QSB3.3 engines that were donated and most of the compression rings were broken. Cummins wants $100 per hole for rings! I found that Chev 305 V8's have the same bore, so we machined the ring grooves to accept the wider chev rings and for $80, we now have rings for two of the Cummins!

What I would love to do is convert an RSX to diesel that really performs!
I'm thinking of a Yanmar 3TNE88 with a turbo should make about 60-70 HP and 200 lb-ft of torque if you tweak the injection pump a little. That should keep up or surpass the stock Piaggio!!

The 'cool' factor of rolling coal in a SXS would be impressive!
 

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Discussion Starter · #17 ·
I have been driving the Gator a lot to shake out any bugs and I've been comparing it's performance to the original Briggs engine. Top speed is basically unchanged. With my Carlisle All Trail tires top speed on level ground is 29 at 4'100 rpm. The big difference is when climbing hills.

My road crosses a river valley a couple miles from home. With the Briggs engine and the pedal to the floor at the bottom and entering the hill at 29mph the speed would soon bleed to about 20 for much of the climb out of the valley. With the new engine I started at the bottom at 25mph and 3'700 rpm and the speed held steady for the climb. I could tell the governor had opened the carburetor but the engine has the power to maintain speed. I've not tried it yet with the pedal to the floor.

So far it seems that idling and short trips are not an issue for the Honda. The exhaust smells as it should, not excessively rich and the oil smells like oil and with no gas smell and the plugs look good. After idling several minutes you can stomp on the throttle and it accelerates smartly without hesitating or missing. I swear Deere would have had a real winner if they had put this engine in the 550.
 

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Honda engine cost a fair amount more. Plus there's the Honda big red and pioneer so it kind of makes it a conflict of interest for both companies.
 

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Discussion Starter · #19 ·
I LOVE this engine. Last night I turned on the lights and just let it idle for 1 1/2 hour while processing deer. The engine never missed. Never blew smoke and never gave any indication that it was fowling or loading up. It just sat there putting away the whole time. What a major difference over the Briggs. At idle I think my front LED's draw about the same as the charging system's output and after idling with the lights on for an hour and a half I did some short trips and it started right up with no indication that the battery was drained.

 
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