Topic: honda gx25cc motors

[dave500]

whos got a honda gx25cc four stroke motor on a weed wacker or other garden power tool?i found a weed wacker missing its cutting head in a skip bin(i drive a skip bintruck as my job),i kept the little four stroke engine as i was intrested in pulling it apart and sussing out the tiny cam and valve arrangement,anyway onced i got it home it turned over ok and had spark,so i checked it had oil put in a little fuel,a few pulls on the starter and it farted,,then a few more and it fired up and ran well etc,,i had plans in my mind to section it to show the four cycle operation but this little engine is perfect,dirty but runs clean and everything,its the intergral head with barrel and upper case design,,i googled the engine to find oil capacity and valve settings etc and have found these motors get fitted to bicycles and model airplanes!they run a belt overhead cam,so ?does this still count as a single overhead cam engine worthy of place here,,i dig the little thing.

[Retro Rocket]

Down sizing mate.......    You'll have fun finding a frame for that one.....

[Terry in Australia]

I've got a little scooter out in the garage with a small Honda 4 stroke engine Dave, my brother in law left it here a couple of years ago so I could fit new chains and sprockets on it, but I couldn't find a supplier, so forgot about it. I'm glad you reminded me, I must pull it out and fix it for the poor bugger! Cheers, Terry. 

[faux fiddy]

capacity and valve settings etc and have found these motors get fitted io [  ] and model airplanes!

I've heard of the two stroke lawn tools used for this.  People I heard of reverse engineered a thrust bearing so the prop wouldn't pull the motor apart.

[trueblue]

Those overhead cam honda brushcutter engines are interesting little buggers, I used to work for the local council in the workshop, and had one of them drop a valve, anyway upon disassembly to inspect the damage I found it only had one cam lobe, the intake and exhaust valves both run off of the same cam lobe, just on opposite sides.

[seanbarney41]

whos got a honda gx25cc four stroke motor on a weed wacker or other garden power tool?i found a weed wacker missing its cutting head in a skip bin(i drive a skip bintruck as my job),i kept the little four stroke engine as i was intrested in pulling it apart and sussing out the tiny cam and valve arrangement,anyway onced i got it home it turned over ok and had spark,so i checked it had oil put in a little fuel,a few pulls on the starter and it farted,,then a few more and it fired up and ran well etc,,i had plans in my mind to section it to show the four cycle operation but this little engine is perfect,dirty but runs clean and everything,its the intergral head with barrel and upper case design,,i googled the engine to find oil capacity and valve settings etc and have found these motors get fitted to bicycles and model airplanes!they run a belt overhead cam,so ?does this still count as a single overhead cam engine worthy of place here,,i dig the little thing.

mount it on a skateboard!

[dave500]

Those overhead cam honda brushcutter engines are interesting little buggers, I used to work for the local council in the workshop, and had one of them drop a valve, anyway upon disassembly to inspect the damage I found it only had one cam lobe, the intake and exhaust valves both run off of the same cam lobe, just on opposite sides.

yeah i checked out that,they run a sort of relay via sub rocker shaft affair,and also have centrifical decompression,,a lot of tech in a tiny throw away engine,today when i was picking up a skip a motorised bicycle went past on the opposite side of the street going easy 70 kays with a deeper sound,,i was thinking,yep him got one of dem honda engines in dat one boy,he might have had the 35 cc version,,a guy was killed here riding one of those home made bike jiggers a few months ago,on the tv news they stressed how its illegal etc.,these are restricted by design of the inlet more than anything,ill bet theres a few hop up tricks that get done to these,a different carb for a start,these have the rotating tube with a hole in it throttle,ive also kept a kawasaki 30cc brush cutter motor that runs,it has a normal slide throttle and needle jet type walbro carb,id like to hook them up together via the same clutch and make them arm wrestle till the loser goes backwards,,,,,who wants to see it on you tube?

[trueblue]

Those overhead cam honda brushcutter engines are interesting little buggers, I used to work for the local council in the workshop, and had one of them drop a valve, anyway upon disassembly to inspect the damage I found it only had one cam lobe, the intake and exhaust valves both run off of the same cam lobe, just on opposite sides.

yeah i checked out that,they run a sort of relay via sub rocker shaft affair,and also have centrifical decompression,,a lot of tech in a tiny throw away engine,today when i was picking up a skip a motorised bicycle went past on the opposite side of the street going easy 70 kays with a deeper sound,,i was thinking,yep him got one of dem honda engines in dat one boy,he might have had the 35 cc version,,a guy was killed here riding one of those home made bike jiggers a few months ago,on the tv news they stressed how its illegal etc.

Yeah I had a copper trying to tell me how it was illegal to have a chainsaw motor attached to the back of my mountain bike when I was a teenager, it was a stihl farm boss engine, the biggest one you could get, I can't remember the size.  That thing would do the best part of 90 kmh, thankfully he didn't charge me with anything, but the mongrel took the sparkplug out of it so I had to pedal the 15km home.

[dave500]

a kids the best we could do before we got real bikes was we found like an old "scott bonner"or the like mower at the local tip,the self drive reel type with the cast iron roller,it had no motor but a cone clutch,we cobbled a two stroke engine on to it and by passed the reduction chain drive down with the chain ending up on a severe angle,we some how attacthed a bit of plank on the rear with wheels to stand on and away we went,it didnt steer,we had to get off and point it in the desired direction,it was great for all the weekend untill the cast iron roller broke to bits,,you shouldave heard the racket we made,it might have done about 20 kays or less per hour,faster than we could run as kids at least.

[trueblue]

I got the use of my cycling coaches metal lathe, and made up a roller that threaded onto the end of the crank, the roller just ran directly on the tyre, the engine even had a clutch I used a clutch lever off of a motorbike and it just simply lifted the roller off of the wheel, to initially start the engine, I just rode along and reached my hand back and pushed down to force the roller onto the tyre, this spun the engine over to get it going, it was a brilliant setup, except it chewed through rear tyres like they were going out of fashion

[dave500]

some people should just buy a motor bike,,although its fun doing these home grown jiggers,although when we were doing this there were no cheap cong wee scooters or the like,used brand x scooters go for nothing now, a proper bike was the sl70,the honda xr75 was the bike to have though,the yammy 60cc  mini enduro was good,we didnt really care so long as it had gears.

[trueblue]

pretty well hit the nail on the head there Dave, after I built that monstrosity, my old man bought me a real bike to ride around our property as long as I wouldn't ride that (as he called it) death trap on the road any more.  It was an old 77 yammy 100cc ag-bike, the slowest heaviest POS I have ever ridden, but it taught me how to not push the limits too far on a bike, because it didn't stop or turn, drum brakes front and rear, it's a wonder I didn't go through more fences than I did on that old girl.  I also learnt not to ride too close to fences, they hurt, especially when the bike stops and you don't.

[dave500]

man the agg with hi/lo was a good bike man?half the power of a non reed elsinsor with the same handling.

[dave500]

rainy day boredom photos

[faux fiddy]

Those overhead cam honda brushcutter engines are interesting little buggers, I used to work for the local council in the workshop, and had one of them drop a valve, anyway upon disassembly to inspect the damage I found it only had one cam lobe, the intake and exhaust valves both run off of the same cam lobe, just on opposite sides.

,ive also kept a kawasaki 30cc brush cutter motor that runs,it has a normal slide throttle and needle jet type walbro carb,id like to hook them up together via the same clutch and make them arm wrestle till the loser goes backwards,,,,,who wants to see it on you tube?

Yes. You tube, I bet $5 US on the honda. The 50cc has torque that will let you go uphill in any gear. Two stroke might win without a load off the line. WHat you are describing is different alltogether, and I bet little enough on honda that it may be not wirth burning up either to have controlled result and honda SOHC will win.

[Terry in Australia]

Have I shown you guy pics of my bike? I got bored a couple of Christmases ago, I'd built a single cylinder bike and a mate bought it, so fully cashed up and with a "Cash Converters" bike to play with, I built this.

My cuz is "tuning" it (he's a brilliant Suzuki trained two stroke tuner) and I'm buying a couple of nitrous kits off EBay for it, and we're hoping to get 100 MPH out of it at Lake Gairdner next year, if it's not underwater as it was this year. Cheers, Terry.

[Retro Rocket]

HAHA I love that bike Terry.....   What tyres are you going to run on that, i imagine getting a blow out on that bike at 100MPH would be quite a spectacle....

[dave500]

you have to do the wipper snipping first,do the edges really nice then mow the lawn and trim the hedges then you can race it!!

[Terry in Australia]

HAHA I love that bike Terry.....   What tyres are you going to run on that, i imagine getting a blow out on that bike at 100MPH would be quite a spectacle....

Well I'm a big fat bastard Mick, so my cuz, who is about half my weight will be riding it, so if we have a blow out, or if he just stacks it, I can go and get help. I had thought about tyres (maybe just some new ones, those tyres are probably 10 years old) but "going to get help" is about the extent of our safety plan so far.

We really should try to discuss our safety plan without alcohol present at least once between now and our salt flats attempt in March next year, I guess? Tyres eh? Thanks for the tip!

[MILO]

I found one of them on the side of the road a while back!

I put it on a pretty big Rc plane, and flew it a few times and then spread the model like soft butter across a paddock hahaha.....

Very cool little engine, theres a place that you can buy hot cams for them too

[dave500]

i didnt notice this sticker before,,we must get the good ones here!?

super duty cam,bigger valves with stronger springs,factory hand finished porting,less restrictive exhaust,optimised carb,cop air filter,cop rip start handle?

[74cb750]

Nice one Dave,
Hey Terry, do you have a parachute for when it throws you in the air?

[Sam Green Racing]

Those overhead cam honda brushcutter engines are interesting little buggers, I used to work for the local council in the workshop, and had one of them drop a valve, anyway upon disassembly to inspect the damage I found it only had one cam lobe, the intake and exhaust valves both run off of the same cam lobe, just on opposite sides.

A really true single overhead cam.

[faux fiddy]

My cuz is "tuning" it (he's a brilliant Suzuki trained two stroke tuner) and I'm buying a couple of nitrous kits off EBay for it, and we're hoping to get 100 MPH out of it at Lake Gairdner next year, if it's not underwater as it was this year. Cheers, Terry.

Wallow out the transfer ports, I'm sure they are restrictive and de-tuned for safety and longivity.  I bet you can make your speed goals.

Tires and chainguards of some  type might be a good idea.