After talking to Al Hodges at PVT I decided to install a high rev kit and a take off carb from a 35hp vanguard onto my 20hp vanguard. With the carb he sold me an adapter and K&N cone filter. I also made a custom exhaust as my old one was rotted out. I finally have everything installed and hooked up.

It starts, a little rougher then stock but I wasn't completely shocked as I advanced the timing ect with the mods. HOWEVER, when it starts I get alot of think black smoke out of the exhaust and even a bit of smoke out the air filter. the smoke then stops until I Really rev the throttle at which time I get think black smoke coming out of the exhaust again.

While I can handle bolt on mods I am far from a mechanic. Any help would be much appreciated.

A while back we put a stock 35 carb on a 23 briggs with headwork and a cam. It did pickup a couple mph and some rpm. The downside is it was always very rich. Afr was usally in the 10.5 to 10.9 range. We thought about trying do downsize jets but instead swapped to fuel injection. Sounds like your is richer than ours.

Yup, black smoke is too much fuel, pull the plugs and look.

What size jet would you suggest going down too? And where would be the best place to purchase?

you need to adjust the idle fuel first and you may have to remove the adjustment limiter, be gentle those screws break easy. As far as jetting im not sure how small you can buy. I would drop 10 to 15 % from stock. Poss pvt, boar dr,or partstree. If u cant find them small enough pm me.

Here is a briggs# for 134 jets.only one is offered for the mid jet . Setting ur idle fuel and running the smaller main should get you in the ballpark

So heres the good goo bad and ugly on this swap. as I did it on my 23.

The good - It fits! bolts right up to the stock intake I chose to port match everything while everything was apart.

The bad - jets are $20+ a piece from pretty much any dealer get quite expensive when trying to dial it in.

The ugly - a word of advise is to just give up now and get the mikuni. I put a mikuni on mine for under $500. There is nt a lot of options with jets for the stock 35 but I was able to get the top end dialed in on the main okay where it wasnt fouling plugs at high rpm. The problem is a pilot jet (idle speed) there is only a 50 and a 52 size. Its way to big even on the cold days below 32 with the smaller jet the motor would load up with fuel and die cough soot out the exhaust it was a pain in the ass trying to dial it in. You could try hotter plugs to help burn off the excess fuel and keep from fouling. I tried a hotter plug and started detonating at high rpms so I would have needed to drill out main jets I was @ 150 & 154 during duck season. What is comes down to is tunability. There is none with this carb. With a mikuni there is such a wide range of jet options to tune the low mid and top range. I did see an increase in speed and rpms with this carb but never could dial it in perfect. Once I got a mikuni and dialed it in I was able to get 2-300 more rpms over the 35 carb and got it dialed in precisely for summer and for duck season. I know I spent over $200 getting the set up rigged up and trying to tune it only to sell the carb for $40 and move up to the mikuni. Save the money and hassle and get a mikuni you will be much happier in the end.

Here is my list a jets available from when i worked on mine if you really want to try dont say I didnt warn you though.


#50 - P/N - 842069

#52 - P/N - 842740

Main Jets: Stock 152,158 or 138,144

#134 - P/N - 843376

#138 - P/N - 843365

#140 - P/N - 843587

#144 - P/N - 842098

#148 - P/N - 842738

#152 - P/N - 842095

#154 - P/N - 842739

#158 - P/N - 844649

Well you warned me.....
• The good - It fits! bolts right up to the stock intake I chose to port match everything while everything was apart.
• The bad – expensive and could have probably bought a used mikuni.

I HAD a stock 20 hp briggs. Here is what I did:
• Rev Kit from CartsPlus
• Custom dual exhaust (one that is often discussed on this side, used the old flanges welded on couplings and screwed in mufflers)
• Stock 35 hp carb with K&N filter and adaptor (from performance V-twins), I then shipped the carb to EC Carburator whom rejetted and adjusted the a/f screws.

Result, sounds strong at full throttle but it ideals high and runs rich. To any one else I agree……Save the money and hassle and get a mikuni you will be much happier in the end.

as the old saying goes you can lead a horse to water but you can make him drink. HAHA I told you exactly what was gonna happen man.

With the larger carb I was at about 4300 rpm out of the water but in water it dropped to max 2300-2400 and seemed to run hot. So I went back to a brand new 20hp carb and now I only get 3600rpm out of water and still 2300 in water and still seems to run hot/overheat. I have new plugs, 2 new coils, good compression….not sure maybe the wrong size prop? Or something else going on?

Take the high rev kit off and see what it does


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Good idea, have nothing else to lose. I will leave the valve shims in from the hi rev kit but put my stock timing key back in.

Thanks!

I would do a leak down test and check for good cam travel myself

And at least make sure the timing key didn't shear

Going to check the timing key tonight.

We already did a leak down test and it was good.

Well hopefully fixed my problem or atleast part of it. Pulled the flywheel tonight to find the aftermarket advanced key from Cartsplus Rev kit which i had installed was sheared. I replaced it with the stock key that I still had laying around. Going to take it for a test run in the water on Thursday after work.

I bet your itchin to go run it

I just can't catch a break with this motor....the new stock timing key def helped. it ran great for a min or so, was getting 3500ish RPM in the water with me and another guy in the boat. Then it started to bog or rev around 3000, I lost some power. Thinking I have an air leak somewhere or need to adjust the a/f mixture?

Only been working on this motor for a couple of months in my minimal free time....that min or so of it running right was the highlight of my summer haha

If the first key sheared it may have sheared the new one,

If you ever run into a key shear, Lap the flywheel to the taper on the crank to ensure a good fit.

The flywheel key that sheared was an advanced timing key from CartPlus so it was much thinner, I put the old stock key back in, much thicker. Guess it wouldn't hurt to pull it apart again and see if this key sheared as well. Seems odd to me that this one would shear but I am far from an expert. thank to everyone for the advice.

The keys are not designed to keep shear from happening. Just to locate flywheel. As maxis said your need to lap flywheel to the crank, then properly torque it down. I have even put a couple drops of locktight on crank before install on one that I had shear years ago

You sure you're getting the flywheel torqued on properly?

Hmm, so we are thinking its still a flywheel key and not a carb/air leak issue?

I borrowed my buddies torque wrench as mine didn't go high enough so I'm fairly sure the flywheel is torqued on correctly. I did not lap the crank/flywheel however.

I will be working on it at night after work this week as the opener here in WI is Saturday morning!

I would order another advance key, those motors really like some timing

okay appears i had an easy fix that I should have caught, but my throttle cable was a little loose as was my governor that goes into the block. runs 3600-3700rpm in the driveway great idles down to 1500rpm. Going to try her in the water again this weekend, fingers crossed. Only non factory parts left on it are a custom duel exhaust, K&N cone filter and the shims rods and retainers for the valves form the rev kit.

Thanks to everyone that offered help during this.

Think I might try another advanced timing key next and or increasing the RPMs adjusting the governor.