XUV 550 Honda Engine Conversion

[Dane]

I am replacing the Briggs & Stratton engine in my XUV 550 Gator with a Honda GX630. Deere spec'd a non standard taper on the Briggs' shaft and drive clutch. In order to stay with a stock engine and clutch I am also replacing the drive clutch with a Team Rapid Response aftermarket clutch.

The engine arrived today and I used the forklift to help lower it in place. It is very similar in overall size to the Briggs but has a more boxy shape.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine1_zpsa5966eb4.jpg

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.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine2_zps2d7f4d0b.jpg

[Dane]

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.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine3_zps52e0a23a.jpg

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.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine4_zps2ca7abd7.jpg

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine5_zpsa81be7bf.jpg

While I had the headers off I did a minor polish of the inlet area but did not spend too much time on it. The sharp bends and varying pipe diameter leads me to think there is not a whole lot to be gained. Still, the stock pipes had some pretty hideous weld bead intruding into the flow path. Easy to manufacture but not so great for letting the engine exhale.

[Dane]

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.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine6_zpsed6f9424.jpg

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. I hope to get the rest of everything put together enough to run the engine and make sure the clutch disengages properly before I go through the hassle of installing the clutch housing.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine7_zpsd16a073c.jpg

The key is fitting too snug so taking it down a bit will be the next project.

[Dane]

Oh, I forgot to mention the irony or silliness of manufacturing. I removed an American engine made in Japan and replaced it with a Japanese engine made in China.

[Bunky]

I am jealous. I wish I had metal working skills.

[GATORDONE]

Can't wait to see the rest of the story!! :lurk:

[Dane]

The problems continue. Even though the overall dimensions of the Honda are very similar to the Briggs it's more squared shape is causing problems. Most recent is bracket and linkage that controls the four wheel drive and differential lock. 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 the addition 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 tried a few things and stick welding with nickel worked best. 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.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine8_zpscabed84f.jpg

And here it is showing the cut out around the engine.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine9_zps9b164b9d.jpg

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.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine10_zpsc6b67b86.jpg

An awful lot of work for a control arm and bracket.

[Dane]

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.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine11_zps571fa041.jpg

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine12_zps49456f7f.jpg

I also re-attached the clutch housing base casting and bottom plastic. The driven clutch is in place and I have the drive clutch on there but don't have a bolt. The one I got is too short and none are available locally. Not much call for 3/8-24 grade 8 bolts over 4" long so... I've ordered 4 bolts. The overnight shipping being three times the cost of the four bolts.

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.

[Dane]

More work on the exhaust heat shield mainly around the front to protect the passenger compartment plastics. 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 don't want a spark catching anything on fire.
http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine13_zps471e9b79.jpg

To the right of the dipstick tube you can see some of the pieces I tacked in place. No fancy fitting or finishing since they will be out of sight and I'm running out of patience.
http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine14_zps238cbc5e.jpg

[Dane]

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.
http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine15_zps474bb27c.jpg

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.
http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine16_zps4baebecc.jpg
http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine17_zps7fdbe9be.jpg

[Dane]

http://i922.photobucket.com/albums/ad67/pilotdane2/ReEngine18_zps7bfad492.jpg

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'll have to make a plate and adapt it to round to accept flex tubing, probably aircraft SKEET or SCAT. I wish I had an easy way to show the carburetor inlet area for the Briggs and Honda next to each other. The difference is amazing.

And for those of you with a 550 you'll notice that the bottom part of the seat frame right above the engine and below the seat belt attachment is missing. The frame interfered by about 1/2" with the front cylinder so out came the sawzall and cutoff wheel.

[Dane]

I'll skip out of order a bit since I found a good way to show the difference in the carburetor inlet area between the Briggs and Honda.

Here is the Briggs carb inlet that comes in the 550. I didn't bother putting a micrometer on it but it's basically an inch! I find it hard to believe that this engine can produce 16 hp breathing in so little air. No wonder it's sensitive to a slightly dirty air filter.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine19_zpsdea600b4.jpg

Here is the adapter plate I made for the Honda placed over the Briggs carburetor inlet. Dramatic difference.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine20_zps63d496b3.jpg

[Dane]

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.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine21_zps7ec64340.jpg

There is 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.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine22_zps13ba8992.jpg

[Dane]

I ordered both SCAT and SCEET tubing just in case. I knew SCAT would make the bends but was not so sure about SCEET which has a silicone lining which SCAT tubing does not. It has a smoother interior but can't bend around as tight a radius. The SCEET works out perfectly.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine23_zps6cc18ff6.jpg

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine24_zpsa431d1ce.jpg

[Dane]

I've had to access the Briggs engine so frequently that I "modified" this plastic a while ago with a sawzall to make removal easier. The piece on the left is supported by three screws and stays in place well and best of all with the cut the plastic that covers the top of the engine can be removed without having to remove the seat/seat belt frame.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine25_zpsba323c7a.jpg

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine26_zpscedbb097.jpg

And finally the re-assembly is almost complete.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/ReEngine27_zps26130304.jpg

[Dane]

The difference in power is instantly noticeable. I left the Honda's governor in place so it tops out 500 rpm short of the Briggs which means top end speed is reduced but acceleration is much stronger. You can just tell that there is more power attached to the other end of the gas pedal.

I realized one thing I totally missed. The interlock that prevents driving through the parking brake. My engine install does not have the interlock so I did a test run with the parking brake on. With the Briggs you could feel the brake holding before the interlock kicked in. The new engine just powered through it like it was not there. The only way I knew was the little red light on the dash.

After more driving I've discovered that I have the dreaded can't shift problem. Some of the time the Gator would creep away after coming to a stop and shifting was difficult. So, I tore the bloody thing apart again. Adjusted the idle speed and verified that the primary clutch is releasing as it should. I talked with my Deere Service Manager and he confirmed that I had the old/original belt. To help address the shifting problem in December of 2013 Deere updated their PIP to include replacing the belt with a thinner one. I have one on order but am not totally confident that will resolve the issue. Tomorrow I'll have to spend some time getting technical and checking my clutch alignment and make sure the engine and transmission shafts are parallel. That should be fun. :Bnghd:

[Dane]

The belt currently on my Gator (M161702) is the old, original one used when the 550 first came out. I have the new M172473 belt on order to see if that helps with the shifting problem.

[Bunky]

Congrats on getting it running. You have all the equipment build a brand new unit.

[Dane]

After taking the bloody thing apart again the culprit is the primary/drive clutch not releasing fully when the engine returns to idle. It will remain fully open when first starting the engine but after reving up it does not fully open at idle. When I turn the engine off it pops open the last 1/4 to 3/8". I've contacted Team and they are sending a new spring to better adjust the clutch to my engine's rpm's.

In the mean time I've taken my Deere clutch apart and put it's spring in and it's working much better. The problem spring is about 3/4" taller and has wire about .050" thinner than that used in the Deere clutch. With the Deere spring in the clutch it's engaging at about 1'700 rpm and the clutch is fully in high gear about 3'000 rpm. There is no further movement at higher rpm's and it seems to be engaging reliably with the idle speed set to 1'100 rpm.

[Dane]

The engine and clutch continue to work well. Last night 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.

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.

I stuck with the existing Deere throttle cable sheath and made a new core. The stock throttle cable has a .050" core which is damn tiny but there is room inside the sheath 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.

[Dane]

I made up a new throttle cable and 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.

[MBDiagMan]

Outstanding project Dane. How many hours did you get from the original B&S engine?

[DIXIEDOG]

Impressive conversion :Thmup:

[Dane]

I am loving the new engine. Last night I needed some working light and the Gator was the mobile lighting platform. I turned on all my forward lights (LED's) and let it idle for an hour and a half. It never missed a beat and never gave any indication that it was loading up or fowling.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Deer/SkinningwGatorLight_zpsee2add63.jpg

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Deer/SkinningwGatorLight2_zps38eefc4e.jpg

[Bunky]

Good to hear. You have to use the tools you have -- loader on the tractor and the Gator for lighting.

[MBDiagMan]

Yeah, how did we manage to gut a deer that we killed at Sunrise before Gator's and Front End Loaders?:BG: Dane, is the deer season already in full swing there or is this a kill in the archery season?

[Dane]

NC is divided into regions and I'm in the central which is currently archery only. Gun season will not open here until mid November. Normally I'd wait for gun season but wifey was in a panic last week when she realized we were out of venison. Tons of alligator and hog but no deer so I had to get to work a little earlier than I had planned.

[MBDiagMan]

That's about the same schedule as the season in Texas. My lovely wife isn't big on cooking game. Her mother was an absolute master at it, but we lost her in 1998. My meat hunting pretty much stopped at that point.

[Dane]

Now it's perfect!

The engine came with governor and linkage system for a pressure washer or cement mixer. It worked reliably but not the best throttle control for a vehicle requiring frequent, precise throttle inputs. The Honda has a double bellcrank system (if you count the governor) which creates a long, circuitous throttle control path, lots of springs and linkages. The linkages and springs provide easy starting and low idle once running but are a bugger when driving around. The bellcrank has a simple steel on steel pivot which is slightly "sticky" for vehicle use. Add in the governor lag and it was not the best driving experience.

I finally broke down and brought the Gator back into the shop and shit canned the stock linkages. I replaced the Gator's stock throttle cable with a Teflon lined auto throttle cable. While it's larger in diameter than the Deere cable it's smooth as butter. Made a control arm to convert the longer throw (cable pull) of the gas pedal to the shorter motion of the carburetor's throttle arm complete with proper bearings at the pivot for smooth long term operation.

Now, the throttle response is much more auto like. No governor, bellcrank and multiple springs mucking between the gas pedal and throttle. Just a nice, butter smooth throttle response.

The trade off? The system on the Honda engine provided adjustment for easy starting. There were two adjustments that allowed you to briefly have one idle position during starting and another after the engine was running. After my mod I've only got a simple idle speed adjustment on the throttle butterfly. It works once the engine is running but I think during winter it will require a tap of the throttle when starting.

[Bunky]

Persistence pays off. It sounds like a great set up.