# Engine problem - fixed-jet carb



## Joel_BC (Nov 10, 2009)

I've got a rototiller that has replaced my very old one... this new one is going into its fourth year of service. Last spring, I noticed it would run great until I engaged the wheels and tines. Then the engine would surge rather than run steadily at high rpm. I found that if I gave the carb a bit of choke (about 25% above minimum or "off" position), it would run more steadily. I concluded it wanted a slightly richer fuel:air mixture.

Trouble is, no adjustable jets (no high-speed, no low-speed). Don't know if this will matter, but it's a Briggs & Stratton 7hp "Intek" VC206. I never even thought to look for adjustable valves or jets on the carb when I bought the machine.

Fuel-line delivery to the carb seems fine. Best I've been able to think of has been to use some carb spray to clean out the passages - and to always make sure I use fresh, clean gas that won't have much H20 in it. But no significant change. I can continue to run the engine with a bit of choke, but it seems like this should not be necessary.

Comments or advice?


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## plowjockey (Aug 18, 2008)

Take the carb apart, clean it thouroughly with carb cleaner, then reassemble.

Spraying carb cleaner in it from the outside, may net get all of the crud and/or dirt.

Also Inteks have adjustable engine valves, that may need checked.

Newer engine don't need adjustable carb jets, IMO. Just clean one's.


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## HermitJohn (May 10, 2002)

All modern small engine carbs are set super lean at factory for pollution reasons. And EPA forced them to do away with any external adjustments. So any tiny air leak or anything and you have problems. Can try replacing carburetor base gasket.

I fought with a 5hp flathead Briggs on my mower for several years, it had a no-adjust float carb. Usually just taking float bowl off and cleaning it would help a lot. Also there got to be a restriction above the inlet to the needle valve. I opened that up in both directions with a drill bit. And that stupid choke linkage... I finally jerry rigged it so I could manually set choke independent of everything else. 

Finally it ran low on oil without me noticing and that was end of its life, was already running on borrowed time, long beyond its designers intentions. Replaced it with a new Honda clone engine which I have lot less trouble with its carb.

Oh and you will find you can probably buy a new replacement carb for your engine but that it will cost as much as a complete clone engine.... Gotta love greed. I wouldnt put lot money into an Intek... The Vanguard is probably only Briggs engine model worth buying anymore and it is made by another company in Japan.


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## HermitJohn (May 10, 2002)

plowjockey said:


> Newer engine don't need adjustable carb jets, IMO. Just clean one's.


So instead of opening main jet a quarter turn, you now have to rebuild the carb multiple times until it runs halfway decent. Yep, gotta love modern engineering improvements. Cause you know its all for your benefit!


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## plowjockey (Aug 18, 2008)

HermitJohn said:


> So instead of opening main jet a quarter turn, you now have to rebuild the carb multiple times until it runs halfway decent. Yep, gotta love modern engineering improvements. Cause you know its all for your benefit!


Other than the float and needle valve, there is no other moving parts, so there is nothing to replace, other than gaskets.

Old carbs were machined and built to relatively loose tolerances, which warranted a manual adjustment. Not so with newer ones.

I have yet to not have a non adjustable unit perform like a champ, with a known clean carb and properly adjusted valves.

Whether it's for my benefit or not, is pretty much moot, anymore.


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## HermitJohn (May 10, 2002)

plowjockey said:


> Other than the float and needle valve, there is no other moving parts, so there is nothing to replace, other than gaskets.
> 
> Old carbs were machined and built to relatively loose tolerances, which warranted a manual adjustment. Not so with newer ones.
> 
> ...


Newer carbs are made to not be that rebuildable. Usually you can clean them, but some of new ones you cant get to some of passages. Many parts are now PLASTIC on cheaper engines, which pretty much makes a carb throwaway. May not be lot moving parts, but jet adjustment isnt for improperly adjusted moving parts. Its to compensate for minor air leaks or minor clogs in tiny passage, that sort of thing. Or just general wear on engine, as engine wears out mechanically, its fuel richness needs change. Sorry, one size does not fit all, no matter how close the tolerances from the factory. Even on old carbs if tiny adjustment of main jet didnt solve problem, you had to rebuild it. Major jet adjustments may let engine run, but not well. Its like running engine with choke closed. And thats why modern carbs either dont have a choke or have a partially disabled choke with hole in middle of choke plate so you cant fully choke the carb. They dont want you running engine with choke partially closed. They dont want consumer doing anything on his own. And yes its a moot point unless you can find an old adjustable carb and adapt it to your modern engine. Course if you want to battle with a modern carb, you can always get a numbered drill bit set and drill jet out incrementally to make it run richer. Lot more hassle than turning a screw, but its still doable.


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## Joel_BC (Nov 10, 2009)

Thanks for the discussion, guys.



plowjockey said:


> Also Inteks have adjustable engine valves, that may need checked.


I decided I should do a valve adjustment. Just can't locate my old feeler gauge. I'll have to borrow one from a neighbor tomorrow.

I'm sure it's been at least two years since the valves were adjusted. They should be 4/1000" from what I understand. But could the gap being loose cause the symptom of a too-lean mixture?


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## bikehealer1 (Oct 8, 2009)

dont forget to check the intake pipe where it mounts to the intake port on the engine. I have a briggs 6 horse push mower that would crank and run well til it would get good and hot then quit. Finally pulled it all apart this year and found the intake pipe loose. made a huge difference in running.


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## Bearfootfarm (Jul 13, 2006)

Try a little Seafoam in your gas.
It will clean those hard to reach places


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## alleyyooper (Apr 22, 2005)

Before I did any thing else I would run a tank of gas with the proper amount of *sea foam *in it. I make it a first on the list of what my engines get every spring after setting empty all winter.

 Al


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## Manny (Dec 26, 2003)

Does it have a fuel filter? Maybe it's a little plugged up.


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## Joel_BC (Nov 10, 2009)

plowjockey said:


> Also Inteks have adjustable engine valves, that may need checked.


Metric or SAE? The owner's manual that comes with the tiller tells me very little about the Intek engine.

I went to adjust the valves yesterday. The adjuster nuts on the rocker arms have little allen set screws in the center. The allen wrenches I have are only SAE sizes - I don't have a _complete_ set of metric ones, and it seemed I didn't have quite the right little wrench for the small size needed for the set screw. The closest size SAE allen wrench I have just slipped when I put enough torque on it.

Does anyone here know whether the Intek series engines actually are made with metric fasteners?


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## plowjockey (Aug 18, 2008)

Joel_BC said:


> Metric or SAE? The owner's manual that comes with the tiller tells me very little about the Intek engine.
> 
> I went to adjust the valves yesterday. The adjuster nuts on the rocker arms have little allen set screws in the center. The allen wrenches I have are only SAE sizes - I don't have a _complete_ set of metric ones, and it seemed I didn't have quite the right little wrench for the small size needed for the set screw. The closest size SAE allen wrench I have just slipped when I put enough torque on it.
> 
> Does anyone here know whether the Intek series engines actually are made with metric fasteners?


I believe they are metric, but it's been a year or so, since I worked on one.

I got the intructions off the Internet. I'll see if I can still find them.


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## Joel_BC (Nov 10, 2009)

Okay, well no worry about that. I thought someone here might know, offhand.

Anyhow, I got into town yesterday (an hour's drive away) - among other things on my list of errands, bought a set of metric allen wrenches. I'll have another go with the valves pretty soon.

Thanks again for the carb advice.


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## Joel_BC (Nov 10, 2009)

Bearfootfarm said:


> Try a little Seafoam in your gas.
> It will clean those hard to reach places


Oh, yeah, while I'm at it... I've never used Seafoam. But since it got a couple of votes on this thread...

Are there any drawbacks to using Seafoam? I mean, using it in the fuel to clean out the carb passages, as well as intake & exhaust valves, etc.

The only real caution I've found through an internet search is that it may not be good to use it to clean a 2-stroke engine, as the engine needs the oil in the fuel mix to lube the engine's parts, and the Seafoam may temporarily mess that up.


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