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25 cc Craftsman mods?

Old 06-15-2010, 06:46 AM
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peng
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Default 25 cc Craftsman mods?

Hey all, i have a 50 inch apache, running a stock 25 cc craftsman weedeater engine. After doing some searches (google), i cant seem to find any one that has modded one of these before.
It is ok on speed aty this point, i think it could be alot faster.does anyone have any knowledge or resources for this engine? i have done port work on regulated kart racing engines before but never played with anything this small or 2 cycle for that matter..HELP!!! PLEASE!????
Old 06-15-2010, 09:05 AM
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rangerfredbob
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Default RE: 25 cc Craftsman mods?

do a search instead for 25cc poulan as that's who makes the engines for craftsman. the best change you can make is to port the exhaust, stock it is probably around 120* where it should be 150*
Old 06-15-2010, 01:53 PM
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Default RE: 25 cc Craftsman mods?

the 26cc crapsman are poulan, the 25cc are homelite.

If the carb and exhaust are on opposite sides of the engine its a homelite.


Check this out:
http://www.modelpowerboat.com/forum/...-rc-engine.htm
Old 06-15-2010, 10:38 PM
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rangerfredbob
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Default RE: 25 cc Craftsman mods?

I haven't ran into a homelite craftsman weedie, all of them that I have (like 5 of them) are poulan. there's the 32cc rear intake and exhaust, and side intake and side exhaust that are usually either 21 or 25cc that come from the featherlite style of poulan/weedeater brand, that style has 18, 19, 21, 24 and 25cc versions, the piston and cylinder from these are interchangable (that is the 2 bolt backplate versions interchange and the 4 bolt backplate versions interchange, not across backplate styles)

either way, increase the exhaust port timing and make a bigger exhaust outlet (at least 1 half inch outlet if not two, remove internal baffles if possible). All cheapie weedeaters have low exhaust port timing with few exceptions, 150* is a good number to shoot for, poulan likes to produce them in the 110-120* range for whatever reason
Old 06-16-2010, 04:42 AM
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MrMikeG
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Default RE: 25 cc Craftsman mods?

Open up the transfers, best mod I did for my weedy. Post a pic of the rod and crank, if it's cheap just fun run it, if it's cast then it might last
Old 06-17-2010, 05:07 PM
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peng
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Default RE: 25 cc Craftsman mods?

well I ran it and tuned the engine a bit but it still doesnt rev very high, the crank is not a through crank and looks like it is pressed sheets... same as the homelite that was in the hull when i got it.. the only difference seemed to be the place ment of the head/ cylinder bolts. they are diagnally placed. things i think i can do without a degree wheel, timing advance, 2-3 degrees, raise the exhaust port, and stuff the case. i need liek a step by step how to video
Old 06-17-2010, 05:23 PM
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Default RE: 25 cc Craftsman mods?

If it has a "plate crank" it won't last long at higher revs at all, I would guess 10-11k would be pushing it's limits. In my opinion you would be better off finding a better engine before you invest any time in mods. Those cranks bend and flex something terrible. Plus one dunking and it will kill the rod and crank pin. Those are called "half cranks" standard in most cheap weedies. It is probably made by Ryobi. It could have an RPM limiting coil as well, most Ryobi's do.
Old 06-17-2010, 09:00 PM
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Default RE: 25 cc Craftsman mods?

easies way to free up rpm? seems that it is over loaded. but it has a sub drive on it.. prather x265 is there a way to bring the nose up out of the water? seems that if it was weighted frther back it might run a bit quicker. i have the prop as far down as i can get it and i thnk that might be part of the problem.. to much water on the prop..? idk not tuned a hull before.. HELP!!!!?
Old 06-18-2010, 09:12 PM
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Default RE: 25 cc Craftsman mods?

well, today,I used a buddies dremel to tear into my Project engine. I took out the separation in the intake runners, but left the very top withe a ramp in it back to flush with the cylinder, on both side, then raised the exhaust a bit, and moved the coild forward as far on the pegs as i could. i thought about taking them out and shaving off the threads near the top to give me more ignition timing. polished every part of the ports i could get to. then put it back together and it runs. got it back in and went to test it but hit a rock it the fisrt foot, so i have to re solder my flex shaft.. Any ides on how to make the solder in there meltand not deform the brass?
this blows these big boat seem to be a lot of hastle..
Old 06-18-2010, 09:30 PM
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Default RE: 25 cc Craftsman mods?

hassle?? not often I have come home from the pond having to do any more than lube the drive and charge the batteries.

Soldering the cable - good directions here - http://www.modelgasboats.com/Magazin...able_Soldering

Old 06-18-2010, 10:07 PM
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Default RE: 25 cc Craftsman mods?

also i have a rotary carb with a HUGE bore.. same pressure whole location, just a HUGE BORE. similar to this.. http://cgi.ebay.com/rc-boat-carby-26...item563d69ddb7
lol would this engine ever run with that carb? there is no choke but it has so much more airflow. would it be worth the hastle of tuning it?
and is tuning it on the stand gonna help me at all for tuning it in the water?
Old 06-18-2010, 11:17 PM
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Default RE: 25 cc Craftsman mods?

you want a carb with about a 11mm venturi diameter for that engine, at most 1/2" for the rpm that engine will turn safely, and make sure there are two mixture needles, the barrel carbs generally aren't very desirable, not very adjustable.
Old 06-20-2010, 11:48 AM
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Default RE: 25 cc Craftsman mods?

ok so on friday, i pulled the cylinder off and did major porting... took out the runner sepatator almost all the way up, but left a about 1/8 inch of material at the top and raped it so the ring wouldnt wear into the ports. raised the exhaust port about 1/16 of an inch and made the port bigger, side to side. to fill out the whole port instead of just 3/4 of the actual port... didnt remove any material from the base of the cylinder to raise the comp ratio. but i advanced the timing a hair... probable 1-2 degree forward. reassembled and it runs... and the crank is 1 cast peice... not the pressed peices like i thought... It sounded alot stronger to.. went to put it in the water and hit a rock and broke the solder holding my flex to the bullet for the stub to be set into..

what should i do from this point?

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