Thread: Maxx 470 issues

I have a Hydramaster MAXX 470 that has been anything but trouble free. Runs rich (black, sooty exhaust and sparkplugs regardless of no brainer stuff like air filter condition etc.) Also electronic throttle control is always acting up without any binding linkage issues. Has anyone ever changed carburetors or gone to manual throttle linkage and eliminated any of these issues?

Shane, wo is the mfg of the engine?

Should be a Briggs/Daihatsu 3 cylinder if I am not mistaken.

In the past Shane, I have taken out the electric governor on these engines and put in a manual throttle; this will not help you, unless the governor is the actual problem of your engine hunting problem; but it is doable. It may bog a little more than if you had the elect. governor intact, but it will operate just fine.

The carbs are very easy to remove and clean/rebuild. In my experience, this particualr engine is picky about it's altitude, so if you live in an area of high altitude you may want to re-jet the carburetor. I live at 5,000+ feet and have had to re-jet this engine more than any others. This might be why the engine is running so rich.

How many hours are on the unit? It could also be time for a valve adjustment.

I can get the high altitude jets and all the parts for this engine, so let me know if I can help you.

-Good Luck!

Great question Rob. Alot of small engine Manufacturers recommend an 86 or 87 octane as far as I know. Thats what most of my customers run in their vans. I dont know what kind of effect a higher octane would have, if any. Ara might be able to answer that one better.

On that note, people should be aware of running a high ethanol in their vans because most small engines are not equipped yet to run gas with high ethanol content.

Chris, doesnt albuquerque fuel run a high ethanol content. Seems like the 80's and 90's it was all ethanol when I lived there.

I think ours is E10???? Not too familiar with all of that. I will have to look through my Tech Bulletins to make sure what the limits on Ethanol are.

The unit has around 1500 hours.The engine is a 3 cylinder Briggs/Daihatsu. I have removed and cleaned the carb several times. We are pretty low in altitude here, nowhere near 5000 feet. I was thinking of ordering a carburetor rebuild kit just to see if that helps. I spoke to a mechanic @ Jon Don who seemed pretty sure it was "the brain" I don't remember the exact name he called the part. For around 1500 bucks I'm hoping to find another solution. Thank You all for your help!

Thanks again to everyone, had a chance to pick up the wrenches yesterday, cleaned the carb (again), found a loose connection on one of the coils, cleaned the sparkplugs, moved the fuel pump (in case a bend I found in the supply line was causing restriction), adjusted the choke cable, and exhaust diverter linkage. Now the engine is running perfectly with the elctronic throttle working fine too!

Woohoo! Great job! Those Briggs/Daihatsu's can be a mofo to figure out sometimes!

Originally Posted by Ara Klujian

Sounds like a good idea swapping out the electric governor. Is there a sensitivity adjustment spring to compensate for the bog? Let me take a wild guess, fixed main jet?

No, the only spring is on the linkage on the electric governor. I guess one could be rigged up??? The bogging really isn't too bad though.

Well it ran great until the air filter got dirty then back to black, sooty plugs...GRRR I was able to cross a K&N from an auto parts store with the factory ones for about 1.5 the price and since they are reusable and claim better airflow maybe problem solved again...

Shane, if I remember correctly Hydramaster mounted the air cleaner towards the back of the engine close to the engine exhaust, etc. Have you checked for exhaust leaks? It is possible that your air filter got dirty so fast because it is drawing engine exhaust. Just a thought.

Yes Ara, it is a liquid cooled engine and it should be around 31-32 HP. And it's got more wiring than you would ever want to see in a cleaning machine!

Yes it is a liquid cooled 31 horse 3 cyl Briggs/Diahatsu and has a rediculous ammount of wiring. The exhaust leak idea is deffinately feasible becaues the airbox is very close to several connections in the exhaust system. This makes sense because the dirty airfilter could cause incomplete combustion, causing dirty exhaust and a dirtier airfilter causing the engine to eventually stop running. I'm going to run this unit myself for about 9 hours a day for the next four or 5 days on a large project. I'm sure I'll have some more insight after that!!!

I can use some help on my HM 470,, I don;t know where the hoses go for plumbing,,, any help will be appreciated,, thanks DENNIS wheecln@cox.net