Weakest link on factory 2.8 motor?

Miniwood

Miniwood

New Member
#1
#1
What broke on your factory engine?

Please, try not to guess but what you have seen is a known is the issue.

I looked at the factory flywheel and thought that it was pretty well built. Actually it looked better than the honda! Any issues with it?

I know the carb has issues but I am more interested in what would break from overreving the 2.8.
 
ttsquirrel

ttsquirrel

New Member
#2
#2
whats the point? if you want more power, change the motor. do you have alot of stock motors laying around so that if one breaks, you have parts? Are you going to fix up the motor with aftermarket parts that aren't available? are you going to use the motor for something else? there is a thread for that issue. i think the weakest point is it is included with the stock doodlebug. BTW, i use the stock motor with a j/s kit and it has been working great for almost two years. i have an extra one sitting around for when the first one breaks. but like i said, almost two years and still running. everyone has used the stocker to learn and now they have grown up enough for the hf clones to be on both the minis.

let us know what you really are planning to do with the stocker hopped up or just post it in the other threads that are already started.

TTS
 
Miniwood

Miniwood

New Member
#3
#3
No point just a question.
ttsquirrel said:
whats the point? if you want more power, change the motor. do you have alot of stock motors laying around so that if one breaks, you have parts? Are you going to fix up the motor with aftermarket parts that aren't available? are you going to use the motor for something else? there is a thread for that issue. i think the weakest point is it is included with the stock doodlebug. BTW, i use the stock motor with a j/s kit and it has been working great for almost two years. i have an extra one sitting around for when the first one breaks. but like i said, almost two years and still running. everyone has used the stocker to learn and now they have grown up enough for the hf clones to be on both the minis.

let us know what you really are planning to do with the stocker hopped up or just post it in the other threads that are already started.

TTS
Click to expand...
 
bigrob

bigrob

#4
#4
Hey miniwood , that is a great question I have two stock engines that seem to work great , in fact one of them runs better than any of my many other engines be it a clone or b&s or tech . It starts easy and will idle down so slow you can allmost see the valves opening and closeing , sometimes I just let it idle when I'm in the shop because it sound so sweet lol.
But I have always wondered how much power you could get out of one
Rob
 
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Camjamsdad

Active Member
#6
#6
I keep reading how bad these little engines are but the one I bought in December pulls hard with a jackshaft. Tops out at 28 on gps. I bought another db off craigslist that the guy bought used in 2007 and still runs. They can't be that bad. Granted you start hauling 200-300 lb full grown men on them and they'd prolly die but for the kids they fly.
 
Clayon

Clayon

#7
#7
The 2.8hp's on the earlier DB30's usually last longer than the ones on the later DB30's. The weak link on the 2.8hp from over revving is definitely the connecting rod, the flywheel is just fine. On my 2.8hp I bypassed the governor and did some other mods and I could hit 32mph and I weigh 160 lbs. The first thing that went on my motor was the crank case bearings, then the connecting rod. If you could get crank case bearing that would fit the 2.8hp that can with stand higher rpm's and make a billet con. rod (you would need machining skills of course) you would be in business.

Next year I graduate and start apprenticing to become a machinist, I would like to have a lathe and a milling machine of my own to work on, and building a billet con. rod for these engines is definitely on my to-do list.
 
bigrob

bigrob

#8
#8
That's where I suspected the weakness would be , I have two dirt bugs with good engines , but would like to find an old beater one to play with and do some mods.
 
Clayon

Clayon

#9
#9
Rob, I got one in the works right now, I am doing all the stuff Mr. Modified did to his 2.8hp plus some other stuff. Hoping to work on it again this summer. :thumbsup:
 
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chazdaddy

New Member
#10
#10
I have several I got used. Haven't broken any yet. At 1st was very cautious, thinking I would blow one up easy, but running them pretty hard now. All run about the same, except one looses power after you run it hard, I guess it is getting too hot. Let it cool off and it is OK again.

I took it apart today, thinking I would find the issue. It looks pretty good on the inside, maybe a little tight on the piston rings. Actually, appears to have little wear, maybe just needs a little more time to loosen up. I plan to put it back together and just run it.

One question: how do you release the valve keepers? :shrug:
 
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chazdaddy

New Member
#12
#12
Wow, torn my whole engine down to see what's wrong and looks great, can't really find anything wrong with it. Then, I was cleaning it all up to put back together and think I found the problem. Gas tank has internal fuel filter, really small that was pretty clogged up.

Makes sense now, start it up, runs great for a while, then looses power. I thought something worn out, but apparently was just running out of gas at the carburetor. :doah:
 
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skife

New Member
#14
#14
i've found so far that the stock carb is the limiting factor, after i built my custom exhaust i have to run it almost full choke to get any power out of it... thinking its time to drill the jet in the carb.
 
Clayon

Clayon

#16
#16
skife said:
i've found so far that the stock carb is the limiting factor, after i built my custom exhaust i have to run it almost full choke to get any power out of it... thinking its time to drill the jet in the carb.
Click to expand...
Just like when you put a air filter and header on a honda clone, you have to re-jet. You should do the same to your 2.8hp, I can't remember what I drilled my jets out to, but I believe that I drilled my idle jet out quite a bit, and my main jet I only drilled one size bigger.
 
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