aquacraft 18

[john schultheis]

hi looking for some simple engine mods for the aquacraft 18 looking to get better performance out of this motor if anyone knows of any let me know thanks

 

[camaroboy383]

john,,,,,pm me,,ill go through it with u i you want....

alden

 

[camaroboy383]

actually u know what,,,,i will post it all here...this is the how to forum after all,,,and frankly im gettin tired of typing it over and over....so this will be a good way to keep it here....give me till tonight and i will post it all here...it will be kind of lengthy but you can pick and choose what u can and dont want to do....

alden

 

[Bill Gibson]

John, be sure to read Aldens recomendations carefully....i garuntee you wont believe the difference in performance you will end up with one of these cheap lil engines........its kinda absurd, and if you take care of the motor it will actually stay together! He did up a coupla mine, and i couldnt be happier with the results.....!

 

[68Bud]

Thanks Alden, looking forward to hearing about your modifications. I will have my pen and note pad at the ready.

Quick question: Will this con-rod work in the AQ .18?

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXGMM5&P=Z

 

[camaroboy383]

no sir it will not....dont bother...... the factory rod is fine if you cross drill it.....i will go through every aspect of this engine... just give me a little time.... i will post tonight...

bill,,, you sir are the man,,thank you for the kind words.... it is kinda amazing how much of a difference a little tweaking can do.....

alden

 

[camaroboy383]

alright,,, i hope your ready to do some reading...... ........ you can choose what you would like to do..........it all helps in one way or another.....here we go!!!

crank case)

with the engine completely disassembled this includes bearings out of the case.....look down the cylinder sleeve bore,,, there is a transfer port in the rear of the case right above the back plate..(rear left corner if the flywheel side of the engine is pointing away from you.) from the factory this port was never fully machined out,,the maching stopped just short of popping through into the crank wieght/backing plate bore... take a dremel tool with a 1/8" ball carbide or other sufficient cutter and clean that last chunk out of there blending it in nicely so that the port is wide open to the crank wieght/backing plate bore..... in a nut shell this is all that needs to be done to the crank case... the exhaust outlet of the case,,(where the exhaust port of the sleeve touches the case) can be ramped just a touch cause your timing will be raised in the sleeve..... im literally talking like .015" in that area where the sleeve port touches the exhaust outlet of the case.... the last step is not necesary,,but aids in free flow......

piston sleeve)

clean the sleeve with soap and water,,,dry it well,,,,,take a black sharpie marker,,,, color all above the tops of all the ports.... about a 1/4" up is fine.... take a dial caliper and lock it at .030".... run one jaw across the top of the ports,, using the upper jaw to scribe a line through the black marker......do this slowly and gently,,repeat that till you can see the scribed line well......be sure to run the caliper right around the corner a bit to give you that port shape in the scribe line......take a dremel and a small straight cylindrical carbide cutter and cut the ports up to the lines you scribed.....IT IS VERY IMPORTANT TO RETAIN THE SHAPE AND ANGLES OF ALL THE PORTS THE BEST YOU CAN... you will notice the boost port and the exhaust port have angles in the top portions of the port....you will also notice the transfer ports have angles in them but they are directed in a horizontal orientation.....KEEP THEM THAT WAY..after all your ports are cut and you are satisfied,,,take a piece of 1200 grit wet/dry sand paper and wrap it around a small wood/plastic dowel,,, sand all your cuts very well making them smooth,,, angle that dowel as to sand the corner of the inner part of the ports you cut...this will radius out the chrome you cut back in the sleeve,,,,you can take your pinky and run it through the bore from the bottom of the sleeve up,,if you feel any hard burs or sharp edges of the ports you cut,,,,,keep going.....IF YOU DO NOT TAKE CARE IN THIS STEP YOU WILL SCORE A PISTON THE FIRST TIME IT TRAVELS PAST THE PORTS... when the port timing is done being raised the .030" you can take a larger piece of 1200 and lightly run it around the outside of the sleeve till the marker is gone...this should pull down any external burrs on the sleeve....

crank)

same black magic marker method,,, and caliper method.... scribe .010" on the opening side of the window,,,and .015" on the closing side of the induction window... (you can determine which is closing and opening sides by thinking about and looking at what direction the engine turns over.....) cut back the window to your marks,,, again 1200 on a dowel and clean all the edges of your cuts,,, you dont have to go nuts,,just be sure its not crazy sharp against you finger.... now when this is finished take and grind or machine the pto pin off of the crank,,,do not grind away any of the connecting rod pin,,if you have to,,leave a couple thousands of the pto pin so you know you wont grind into the con rod pin......(there is a reason for this and i will explain in the back plate portion)

back plate)

you can purchase a o.s cv-r .18 back plate to install...(this converts the engine to belt start) this is a significant mod in respects to freeing up rotational mass and parasitic drag...... .018" lip...at the oring land.. take it all the way off... the cvr has a bigger back plate opening... listen to me when i say this... when you machine the pto pin off the crank,,,do not,.,,, i repeat do not start taking the rod pin away..... the more you pull away from that area the more the rod will ride off of it....BOOM!...... take the pto pin just to the face of the rod pin..... even if you leave a couple thou...your good...... assemble the crank into the case.. install the back plate with a aqua gasket like 68 bud said..make sure your collet and flywheel are tight..now check the clearance between the crank pin and the back plate...push in on the crank lightlywhen doing so .... with you can do this easily with the p/l out and peek through the liner case bore........if for any reason it touches the back plate...no good..... actually take away the inner face of the back plate,,not the crank.... repeat the process till you have clearance of like .004" remember this is with you pushing in on the crank lightly to be sure the crank is as far as it can slide back with a collet and flywheel tight....... the inner face of the back plate should be smoothed anyway as its rough cast and the rod is gonna ride on it,,, ill garantee you that...... now the tricky part.... to prevent rod float,, spacers,,,,yep i said it,,,spacers can be used on the piston pin to prevent so much rod travel...... didnt matter when the rod was sandwiched inbetween the crank pin shoulder and the pto plate from the factory........ its not necesary,, but it will gain you that lil extra friction free rotation.....

also look down into the back plate,,, the rear transfer will be almost blocked by the back plate,,, ramp that section of the back plate so it smoothly runs up to the transfer port.....

connecting rod)

take a very small drill bit... the same size as the hole in the bottom ends of the rod... pick an end and a side.... the rod is squared so it does not matter wich end or side you choose....... drill a hole into the rod at a 30 degree angle starting in the center of the rod right where the rod is machined like a step above the bushing... drill through into the bushing and into the bushing bore... now clean the bushing where the drill bit popped through with 1200 paper....you can actually take and lightly run 1200 on the inside of the bushing to add a little clearance.....dont go nuts,,just a couple swipes..... the cross drilled hole now faces the crank window.... the fuel will splash right into the oiling hole and prevent the rod from high rpm failure... the factory oil holes are no good at high rpm,,,there is no puddle in the case for the hole to splash in.....

head button)

you will need a lathe or have access to a lathe for this......you want a total bubble volume of .17cc with a k&b 1L or hp plug...(the reason for that plug is the coil housing hole is smaller in cc than any other plug i know of.......1 degree squish band... flat will work also,,but ive found 1 degree of squish angle is easier on plugs,,and showed less signs of detonation..... your goal is to set your head clearance at .008" all of the measurements must be taken by you to accomplish this....... if the bubble volume and squish change intimiadates you then you can just cut the outer section to drop you down to the .008" head clearance......

carb)

pull the carb completely apart.... take a dremel and cone shaped carbide and open up the barrel so that it matches the throat of the carb..... you will notice the barrel opening is smaller than the carb body throat....make them match at full open so there is no flow obstruction... bell mouth the outlet of the carb throat...... and if you have a lathe the mouth of the carb can be cut back all the way to the carb body in the same angle as stock.... or you can shorten the mouth right to the point of the shoulder then put an eliptical shape on the mouth.... either way is better than stock.... shortening the inlet tract does help... the two screws that hold the carb on need washers under them,,, the thicker the better,,, you want them to not stick into the throat of the carb.... the washers will step the ends of the screws out so there will be no obstruction in flow in the throat.....

run a hot plug and restrict your water outlet to .050".... you want to cool with fuel..the more heat the more fuel it can burn and the faster it can go.......

I always recommend that the bearings be changed after they have been pulled from the case.... last thing you need is a rear bearing failing.... its worth the 8 dollars to replace it..... the front one is up to you,,,at least if it does go bad,,,it cant completely lunch the engine...

all of these mods are the same on all my aqua engines i do,,, except the head buttons.... these numbers depend on percentage of fuel......all figures above are for 50% or higher... if lower than 50% will be used you need to raise the bubble volume slightly..17.5 -.18cc will be sufficient.....this goes back to the leaving the bubble and squish alone and just dropping the head space down...the factory bubble is great for 30%

again,,, you can choose what you are capable of doing.... i hope this helps anyone wanting to do mods to the aqua .18...

Alden

 

[john schultheis]

Thanks i'm gonana give some of these a try and see what happens