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Mike Maroni
Advanced Member
Username: Micmac
Post Number: 133
Registered: 07-2005
Posted From: 162.83.107.244
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, June 04, 2007 - 06:43 pm: | 
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Well I've been spending some time looking over the options available to increase performance in the engine area of my Max IV. I currently have a Briggs 16hp vanguard that is stock. I stumbled on a couple of web sites that are dedicated to engine performance products:
First a disclaimer: I don't have any experience or affiliation with any of these folks these are just some sites I have come across and thought I would post them for anyone in the same position I'm in.
http://www.performancevtwins.com/ this is Al Hodges web site dedicated to vanguard engines used for kart racing
http://www.heymow.com/ This site is dedicated to the sport of lawnmower racing (I laughed too) however these dudes are serious about their sport and even more so about engine performance. They have a forum dedicated to Vanguard performance. After all most people snicker about 6 wheelers too! I guess we're all just "one off" brothers in arms!
http://www.eccarburetors.com/ This site also carries small engine performance parts. The vanguard guru is a guy named George Herrin he corresponds on the Heymow website quite a bit.
Anyhow I wanted to start this discussion because I have some questions about the terminology used and some additional tech questions. |
Mike Maroni
Advanced Member
Username: Micmac
Post Number: 134
Registered: 07-2005
Posted From: 162.83.107.244
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, June 04, 2007 - 06:46 pm: |
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Part 2
First off I was out riding the other day and realized my only problem with the 16hp is a lack of acceleration going up hills and a lack of tire speed or spin in mud and even floating. I see some machines shoot up a rooster tail of water while floating. My machine wouldn't make a rooster tail if I drove through a chicken pen!
Otherwise the engine seems to have adequate low end torque from a stand still.
So my question is what would help with the acceleration and tire spin? The obvious answer would be to put in a larger HP engine but that is fairly costly. The other thing with a higher hp engine would you see anymore tire spin due to the fact that you are still limited by the 3600 rpm governor on the engine? (I know the 2 stoke crowd is snickering now!!)
Now getting into the performance mods the one thing seems to be first is the Rev Kit sold by the performance companies. I have a couple of questions about them: The obviously allow you to put in beefier parts to allow the engine to rev higher usually ungoverned. After installing the rev kit is there a way to set the governor higher say around 4500 rpm to get more but allow the safety of being governed? Also one kit comes with an advanced key ignition what does this do and how does it work?
Now onto making the engine breath better: how good is the stock carb for performance? I see that the larger Briggs engines have 2 barrel carbs can these be adapted the smaller 16 hp or would it be better to put a different carb like Brandon had done in his old Max II:
http://www.realatv.homestead.com/BriggsMods.html
I guess the exhaust should also be addressed. The one I have on my machine is poorly rigged and I'm sure that limits the performance of my machine. The previous owner used a forward exit exhaust and welded a pipe back around to exit the rear of the machine not exactly optimal. Where would you find someone to make a custom exhaust for a small engine? I would like to keep a muffler as well although it limits performance. Would a welding shop be able to fabricate something with larger pipes?
The main reasons I'm considering keeping the 16 and doing engine mods are: 1) I alredy have the engine 2)I would like a slight incease performance i'm not trying to build a fire breathing track turning moster 3) I think it would be fun to learn more about the inner working of these small engines.
I apologize for some of the basic questions but you have to start somewhere... I appreciate any input on this topic. Thanks to Roger Smith for some the info he sent me earlier.
Mike |
Rogersmith
Advanced Member
Username: Rogersmith
Post Number: 292
Registered: 01-2005
Posted From: 75.50.23.42
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, June 04, 2007 - 09:54 pm: |
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You've been busy, Mike. As you know Heymow.com is where I hit the jackpot for information, people, and parts. Basically George who works for E.C. spent the time to enlighten me and supplied the parts and other suppliers(cam grinding). Since I'm a mechanic he could give me the short story without spending a really long time on the phone.
He's a busy guy so I'd rather you guys ask me any questions and if you want to build something then buy through him. Also the Heymow website is trying to clean up the forums to attract sponsors and stay on topic about professional mower racing. So I don't talk 6x6 over there.. well I did my thing before the forum cleanup.. it's all in the archives if you read back a year. Just read the vanguard section. There's also a kohler forum. Keep in mind they are generally vertical crankshaft oriented for their sport.
Thanks for the link to Brandon's page, havn't seen it in a long time. The thin head gasket and shaving the head is a popular move. Briggs makes a .040 composite and a .010 shim gasket used on earlier models. E.C. makes a better quality thin gasket. I didn't shave the head or use a thin gasket, instead the rods I bought were an 1/8" longer, and I shaved the 1/8" dish off the piston tops. George said go ahead and shave heads and use thin gasket along with the rods/pistons mod, but I chose not to go all out on compression. Maybe later  But if your pistons and bore are ok then the head shave and thin gasket is a low cost mod. The stock rods are good to 5000 rpm and should handle a stock cammed engine which isn't making power over 4000 anyway.
The briggs 2 bbl off a 20 hp should fit, but expensive. Brandon's spare mikuni looks like the budget performer. EXHAUST! Don't overlook this. In general, 12 to 15" of 1" primary header pipes is what makes power on the dyno for an average vanguard. 2 into 1 collector makes more midrange torque than straight pipes, although good collector design is an art. Look on the internet! I found Harley aftermarket pipe makers the best source.. since we're both working with eneven firing v twins. They like to make the rear cylinder pipe longer because of this. (rear cylinder on argo. Front cylinder/closest to front of vehicle on max) |
Eddie L. Beddingfield
Member
Username: Argo2003
Post Number: 49
Registered: 08-2006
Posted From: 207.117.33.135
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 07:26 am: |
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Mike,You should get someone to adjust your governor out ot 4400-4500 RPM range .It only takes a couple of minutes to do,you need a tiny tach or handheld unit and a tang bender.This will make a noticeable improvement with no cost.Reliability will not suffer as long as you dont get to much above these RPM's. You should also remove the precleaner and also look at removing some baffling in the exhaust.(Pretty easy on some mufflers). |
liflod
Advanced Member
Username: Liflod
Post Number: 149
Registered: 01-2005
Posted From: 151.201.211.103
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 07:33 am: |
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Can anyone provide pictures or step by step instructions to by-pass the governer on my Vanguard? I want to be able to convert back to normal governer operation without alot of effort. I'm trying to get the throttle to operate with alot less effort than is required right now. My kids have a hard time squeezing the throttle and after a few hours of riding , my hand gets tired. |
Mike Maroni
Advanced Member
Username: Micmac
Post Number: 135
Registered: 07-2005
Posted From: 162.83.107.244
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 09:01 am: |
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Roger and Eddie thanks for the info
Roger, your right about those folks at Haymow they are pretty militant about keeping the forum just about racing mowers! There is a lot of info on their site however.
Roger what was the purpose of getting the longer rods the shaving the heads of the pistons? Is the purpose of the longer rods to bring the piston higher into the combustion chamber for more compression? If so if you shave the top of the piston are you eliminating your gain? Also what prevents the valves from hitting the top of the piston how do you know if you will have enough clearance when you do things like shave the head, increase the rod length, and use a thinner gasket?
Concerning exhaust how would you tie the 1 inch pipe to the exhaust ports on the engine? Do you weld short pieces of the original manifold (The mounting parts)?
Eddie - Concerning the governor adustment would my local small engine / lawn mower shop be able to do this? |
Tom Arch
Junior Member
Username: Tomarch
Post Number: 17
Registered: 07-2006
Posted From: 72.75.206.137
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 10:15 am: |
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Lance, I have a max IV with a 25 kohler and the thottle pulls hard also. My freind has a max II with a 25 kohler and the thottle pulls very easy. My max II with a 16 briggs pulls easy. I think hard thottle is just a bad trate in the max IV, every one I have driven pulls hard |
Eddie L. Beddingfield
Member
Username: Argo2003
Post Number: 50
Registered: 08-2006
Posted From: 207.117.33.135
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 10:44 am: |
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Mike, I recommend the tiny tach,and a V-twin manual.This will let you make those adjustments without taking it anywhere.It will also give you the proper valve adjustment procedure and all major rebuild info.You can make a tang tool out of some keystock with a bend on the end and a hacksaw cut in one end.I tryed to set mine as close to 4500 as possible and got 4440,anymore bend and I get the governor surge.I dont think the governor quite knows what to do any higher RPM.To help on flow you can debur the header pipe to match the ports better also(some times this is not a perfect match).I will also recommend a better plug. I hope this gets you started on how to get a little more out of what you already have without relying on a small engine shop. They sometimes have the lawnmower way of thinking,3600 or your warranty will not be any good.That figure is only a calculated # for blade speed.In other words they usuall dont like to stray from factory settings. |
Eddie L. Beddingfield
Intermediate Member
Username: Argo2003
Post Number: 51
Registered: 08-2006
Posted From: 207.117.33.135
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 10:49 am: |
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Lance, look at the return spring,it might be a little stiff.I ran into the same problem on my AV-4(uses the same setup as Max).The return was way overkill,I called the factory and told them of the fatigue I was having and they sent out a lighter spring.It still closes the throttle perfectly and reduces the pressure on the lever. |
Rogersmith
Advanced Member
Username: Rogersmith
Post Number: 293
Registered: 01-2005
Posted From: 70.234.156.129
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 11:07 am: |
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What I said about front/rear cylinder on max's was wrong, obviously. The engine faces the same direction as argo. So the rear cylinder/longer pipe would be to the rear of both vehicles. I'd try 12" on the front and 15" on the rear. That's if brought together into a collector. Otherwise straight pipes/seperate mufflers-silencers keep at equal length. I couldn't find a source for header flanges so made my own. There's a short piece of split tube in the exhaust port used for alignment, leave it out.
The aftermarket rods come in two lengths. Std and + 1/8". The briggs rod length ratio is short to begin with, and the longer rod lets you use a stock piston and raise the compression. I'm sure it varies, but my 18hp piston was about .040 below deck height and also had about .080 dish in the top, so cutting the high perimeter off the piston makes it a flat top and the longer rod moves it up to deck height. So if you have a good cylinder and piston the longer rod gives you a compression increase for free, besides a stronger rod which will stay together at rpm.
Mike e mailed me some time ago and we both agreed the 16hp was too small to push the maxIV the way he wanted, or rather the $ it would cost would buy a 23hp with a 20/50 amp charging system that'd run on pump gas. But he's still curious. |
Rogersmith
Advanced Member
Username: Rogersmith
Post Number: 294
Registered: 01-2005
Posted From: 70.234.156.129
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 11:19 am: |
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That offset flywheel key is how you advance ignition timing. Heymow gurus say a stock cammed engine doesn't need more than a couple more degrees at most. Stock is around 17 degrees. If you remove 1/2 the key thickness like the one pictured at performance v twins, that gives you around 30-36, so there's a conflict of theories between camps. With an aftermarket cam, the key works well.
A guy has to decide what he wants to tolerate in the end before he starts. How much to spend and do you want to use fuel above common pump gas. A thin head gasket is just about all you can go and still run 91 octane. Maybe .020 off the head too like Brandon did. Also the intake manifold will get hard to fit beyond that. People also put small chamber 16 hp heads on an 18, and you can stroke a 16 with a crank from a 18/20. If you have a pile of spare parts around it might be fun. Those mower racers were limited to 20 hp blocks for some time, so that's why their focus is on 14-20 hp engines. But if a guy is going to pay labor on engine build, machine work, custom exhaust, $800-1000 on parts and a starter, a stock 23hp that runs on pump gas would be adequate. Of course a 23 is a good place to start modifications
Lance, do you want the kids to drive it ungoverned? What I did was disconnect the govenor from the bellcrank, connect the throttle to the top of the bellcrank and make a rod from the carb to the bottom of the bellcrank. If that's what you want I'll get a pic. For argo owners, that also got me full throttle travel with about a 1/3 less twist, and no slack or extra play. Hooked direct, the throttle is very responsive, but can be touchy, and you don't have the govenor to add throttle for you under increased load. Also the governor lever needs some spring tension left on it to pull it in towards the engine if it's disconnected. As the guys mentioned, the cable and linkage needs to be free and lubed well to allow a lower pressure return spring. But maybe not so safe for the kids? something to keep in mind. Probably depends on the kid, hehe. |
liflod
Advanced Member
Username: Liflod
Post Number: 150
Registered: 01-2005
Posted From: 151.201.211.103
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 11:53 am: |
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Yes Roger , send me a picture. My Attexi did not have a governer.
I don't think there is a return spring on the throttle. The spring pressure is between the governer arm and the bell crank. When pulling the throttle, the opposing foce is the governer. I looked into changing the arm length of the bell crank to make it easier on the hand. I think I need to weld a tab on the bell crank to get the leverage to my advantage. Right now, the kids pull all their might to get the machine to go and give it full throttle and then let go completely and then do it again and then let go and then do it again and then let go..... |
Mike Maroni
Advanced Member
Username: Micmac
Post Number: 136
Registered: 07-2005
Posted From: 67.142.130.52
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 12:17 pm: |
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Roger,
Your right about being curios I hope it doesn't kill the cat 
I really appreciate the info you have sent me. I do agree the best scenario would be to buy a 23 hp and be done with it. It's just my nature to tinker with stuff. I'm the kid that would take his toys apart the day after X-mas to see if I could make them work better.
Most of all I want to learn more about tuning these engines especially the terms and functions of some of the parts I'm unfamiliar with. I figured I would start a thread for people that have a basic understanding but are interested in more in-depth knowledge. I think the info has been great so far and I hope this discussion keeps going.
After we had emailed I took my max out and was thinking "you know it's not all that bad it just needs a bit more umph" also I had a bit of time on my hands last week and started looking around hence my discovery of those websites.
Here is what I'm thinking - how about doing what you recommended a thinner head gasket and opening up the exauhst, setting the governor higher, combined with a REV kit. That would only be a few hundred $ and I'd see if I'd come close to what I'd like to see for performance.
If you get a chance could you either send or post a picture of the the governor bypass you did?
Thanks
Mike |
Mike Maroni
Advanced Member
Username: Micmac
Post Number: 137
Registered: 07-2005
Posted From: 67.142.130.52
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 12:23 pm: |
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Eddie,
What kind of tach do you mean is there some sort of hand held tach that I could buy or rent that would hook up to the engine? Where does it hook up?. If you could send or post a pic of your tang tool that would be much appreciated. I agree that it would be difficult to get a shop to adjust something out recommended tolerances and I would like to learn to do it myself.
Thanks
Mike |
Rogersmith
Advanced Member
Username: Rogersmith
Post Number: 295
Registered: 01-2005
Posted From: 71.153.183.87
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 05, 2007 - 04:59 pm: |
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I went out for a pic of the throttle linkage but can't see it without pulling the bracket off the heads.. so for now will just say: I drilled a hole in the lower bellcrank in the area where the two tangs are bent downward, and made a piece of linkage from coat hangar, replacing the stock link from govenor to carb. I've had the govenor lever removed off the shaft for years so can't remember how it was arranged. I think Jon Hoath might have some ideas on the briggs governor as well as the 23 kohler.. he moved the spring on his 23 max II for a moderate increase.. but he doesn't have internet access. Lance, I can't tell you how to mod the govenor and springs to fix your throttle effort, but think you're a good enough technician to figure it out if you delve into it. I went direct linkage not so much for higher rpms but to take the "middle man" out of the equasion, IE slack.
Mike, your ideas sound good, might even get away without the rev kit using the govenor. E.C. springs and retainers would save some $ over the rev kit. Just use the outer springs only. And buy two stock steel pushrods to replace the skinny aluminum intakes pushrods. |
Eddie L. Beddingfield
Intermediate Member
Username: Argo2003
Post Number: 53
Registered: 08-2006
Posted From: 152.163.100.132
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 06, 2007 - 09:39 am: |
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Mike ,The Tiny Tach is a name brand of tachometer,it is digital with a built in hourmeter.It is an easy hookup,It has two leads,wrap 1 around the #1 plug wire,the other is a ground.Any small engine shop or northern tool has these.The tang tool is pictured in the manual,and I made one from that pic.(the manual is an actual B&S v-Twin Manual). |
liflod
Advanced Member
Username: Liflod
Post Number: 152
Registered: 01-2005
Posted From: 151.201.211.103
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 07, 2007 - 10:42 am: |
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I looked at my governer set up last night and I think I figured an easy way to gain leverage for the throttle cable. I can mount a small piece of angle on the rear of the bell crank to extend the point of hook-up for the throttle cable. The top part of the angle will pass over top of the existing hole where I can put one screw to hold the angle. I will drill a hole in the vertical section on the rear of the bell crank to place another screw. Should be a 20 minute job when I get a chance.I'll post some pictures when I get it done. |
Mike Maroni
Advanced Member
Username: Micmac
Post Number: 138
Registered: 07-2005
Posted From: 72.255.50.149
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 07, 2007 - 07:20 pm: |
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Eddie,
Thanks for the info I'll pick up both when I get a chance |
Mike Maroni
Advanced Member
Username: Micmac
Post Number: 139
Registered: 07-2005
Posted From: 67.142.130.32
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 19, 2007 - 01:40 pm: |
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Now to add fuel to the fire (pun intended) I happened to get a couple of free mikuni carbs from an old snowmobile (mid 90's Cougar) from what I can tell the are either 32 or 34mm "round slide" vm carbs. My idea is to convert to use on each individual cylinder.
Would this be too much carb for this engine?
Should I use just one and adapt it to the stock
manifold?
These came off a 2 stroke would I need to convert the main fuel system from the primary type to the bleed type for four stroke as per the mikuni manual?
Any ideas were to get intake manifold adapters to do this?
The Jet possibilities and combinations are endless for these carbs. Where would I start to figure out the most optimal jetting for this application? |
Rogersmith
Advanced Member
Username: Rogersmith
Post Number: 304
Registered: 01-2005
Posted From: 70.234.111.36
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 19, 2007 - 04:11 pm: |
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You're doing a good job of keeping the thread active
Probably more carb than it needs but if you want to play, why not. I'd experiment on a budget, and build prototypes out of pvc. You can always go Brandon's style first. Twin carbs won't be a problem as even the factory briggs 2 barrel isolates the barrels to seperate cylinders. Probably seperate tuned ports work better than a one barrel sitting in the middle of a T shaped intake. There's a lot to be gained in intake and exhaust. Velocity is important, the rush of the intake pulse can be 60 MPH, can help fill the cylinder even as the piston has begun rising. Exhaust velocity important too, the tail end of the pulse can have a low or negative pressure helping to extract exhaust and get fresh charge in (4 stroke). Too large intake or exhaust kills velocity. You want the smallest runners that don't limit a particular engines top end. All that said to give you an idea about intakes. Match the intake port D shape by heating the pvc. Experiment with different length intake runners. Run them straight out from the engine if you have room. Take the engine cowling off during prototype, but don't run long and hard to avoid the cyl heads getting hot.
The carbs themselves, can't say. Read the plugs and start rich, or get an exhaust temperature sensor like the guys at heymow talk about.
Performance v twins has manifolds, they are short and the ports look like 23 hp heads which wouldn't fit.
That ought to keep ya busy |
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