Looking to rebuild one for my blaster engines and since I m replacing bottom...

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Looking to rebuild one for my blaster engines and since I'm replacing bottom and top end, could anyone tell me the best set up to do? Like to big bore it whole 9 yards.

%d comments
  • Big bore really depends on needs/wants. Can get a lot of power with a good pipe and port work. But as far as rebuild goes, I'd recommend a vitos stuffer crank and weisco piston/top end kit.

  • If you do decide to port your oem jug, which i recommend, id also advance the timing +3 or +4 depending on pipe and port work done.

  • I was looking at the hot rob 4+mm crank bottom end kit

  • That will require trenching of the cases. Also not really worth it unless it's ported. That's where the real noticeable power lies. You will likely also suffer maximum rpm loss as a longer rod takes longer to cycle. Not drastic, but with a top end pipe could be noticeable. I also have no experience with hot rods. My vitos stuffer crank has been in for 10yrs.

  • I plan on having work done to the top end I was looking at the 240 bore kit from vitos just weighing in the options before I drop big bucks on my rebuild

  • It's a decent kit once it's ported. The ct240 jug is far superior. Both big bore kits will be complimented by the toomey b1 pipe or any right bend pipe. Ct kit comes with everything. If you get just the 240 jug from vitos, I'd recommend a larger carb as well. Ct is really the way to go if going big bore.

  • I have a B1 fatty and toomey pipe, also have procircut set up. I have two bikes it time to rebuild on of them and I wanna lower it, extend it put spacers on it.

  • For the extra $$$$ for me the + 4 crank is a no,

    Case trenching, thinner cases, extra wear , I am not an advocate of stroking, cc's are not the end all of performance.

    A good ported 232 cylinder married to a top quality pipe would meet my needs adequately.

  • Buy a bigger bike...

  • The best performance per dollar is a 3mil crank and proper porting on your cylinder with a matching combustion chamber.

  • Vito's.....

    3mm stroker crank kit

    Superstock piston kit.

    Jet kit

    Clutch kit

    That is as cheap as it gets and extra 10hp.

    No need for porting or head work to use these performance parts. No need for pipes or bigger carbs either.

    Cheap , fast, reliable

  • Of the head is properly cut there is no need to advance the spark timing. Just a fyi.

  • Mine is. I did it for the added throttle response.

  • The fast part is debatable

  • Geoff Harrison

  • OMG the mind boggles, since when has a jet kit and a clutch kit ever increased HP...

  • I thought that too. +3mil adds 10hp with a super stock piston???

  • 3mm stroker crank adds 5hp with the base plate to raise the cylinder

    the ss piston is the same as raising the exhaust port 2mm

    the piston crown is also 2.5mm taller so no loss of compression.

    In fact put it all together and there is .005" less squish clearance .

    88-02 used fatter profile needle the 03+ all blasters came from factory with 220 and 230 main jets.

    Almost every dealership used the 230 just for reliability in colder weather

    There is a 2 hp difference just switching to the better needle profile and the leaner jetting.

    Put it together there is up to 10 hp increase.. the clutch kit has 20% heavier springs and help put the power to the wheels more efficiently

  • Oh wait....never mind

    Yeah.... none of these mods do anything for power..

  • Terry Preston

    You of all people should know proper jetting can greatly affect power output.

  • I don't doubt that those mods will increase horsepower... however 10hp increase without increasing the amount of fuel/air in and exhaust out is very questionable. I would imagine with a good pipe and removal of airbox lid you may obtain close to that. But a jet kit by no means adds power, as jetting an engine correctly is essential, and jet kits typically contain jets that aren't nearly as high of quality as genuine mikuni or keihin jets.

  • Adding stroke yields more power then adding bore. A properly built stock bore cylinder stroker engine will walk all over a stock stroke big bore that's properly built. But I agree that the +4 is a no go for the same reasons, case trenching and thinner weaker cases

  • Never use a jet kit, you seldom get any jets in the range that you need, the sizes are usually wrong and the needle is only good enough to bang into the door to hang your hat on,

    Why would you use a bandaid method of raising the exhaust port with a cut away piston and providing sharp edges on the piston crown to invite melting.

    Porting a cylinder both exhaust and intake is by far the best method.

    Good porting with a re chambered head is much more effective.

  • Never use a "Super-Stock" piston

  • Proper porting and head chambering will get you WAY more power than a shitty piston that fucks up the squish band will ever do.

  • My reasons for not liking stroking is the extra distance the piston has to travel which promotes more wear.

    I have always been under the impression that an over square engine is far better in the torque department.

  • Terry the cut pistons were common back in the day. This is known as "pie cutting" this was when porting (mainly piston port engines) was more of an art then a science.

    The short answer is that it may give some gains, but like everything there are better options. It will make the engine very peaky as it raises the exhaust port and not the transfers. The "wrong pipe" will amplify these effects.

  • i have been there Pat, I was Pie cutting Pistons way back in the 60's

  • The Vito's jet kit comes with the oem 03 needle. The 88-02 needle profile was too fat and too big of adjustments with the clip

    Also oem 270 280 290 300 310 320 jets

    Different pilot jet if needed.

    I never said it was better then actual porting I said it was cheaper and faster then using stock parts.

    As for the cut out Terry

    On a stock blaster cylinder the piston does not drop below the port floor. Apparently you have never put a degree wheel on a blaster and mapped the port timing. It's awful.

    Its bad design as it's it's always in the "heat" and dosent open the port fully. By lowering the rings on the new piston design and cutting the piston on the exhaust side to allow it to drop to the port floor you end up with advanced port timing , longer port duration and allows the piston to escape the heat of the combustion better. This is a big increase in power and reliability.

    Back in the old days people cut pistons on stock engines but this caused the pistons to break due to the rings being too close to the edge. The ss pistons have lower ring grooves for increased reliability and taller combustion dome to correct the loss of compression and the blasters narrow u never squish area.

    A peaky pipe wouldn't be a great idea

    But the oem pipe works extremely well with the stroker crank with stuffer and oem carb with air box lid removed.

  • You are preaching to the converted Steve..

    Been there, done that , moved on...

  • The engine is still over square, your over square by 6mm at the minimum, your not increasing wear on anything really, the rod is even still the same size as stock, only difference is the crank pin is moved outwards.

  • Wisco 240cc run klots racing oil

  • If you are running a longer stroke and the rod is the same length then you will need a special piston with a higher wrist pin height. If wrist pin height is not moved up then the piston will take up all your squish clearance and hit the head at TDC. The only other way to prevent this is a shorter rod or cylinder base plate.

  • longer stroke motors also will have faster piston speeds from 45° ATDC to 120°ATDC and 225°BTDC to 315°BTDC so RPM's become decreased because of torsional rod loads and moment of inertia on the piston because of higher acceleration and deceleration rates. frictional horsepower loss is also higher as piston side load increases if stroke is increased but wrist pin height is not do to the increased geometry on the rod at 90°BTDC AND ATDC.

  • Terry, this isn't directly blaster related, but, in 1987 Honda changed from a short rod to a long rod on their 250R line. The new rod was 4.7(?) mm longer.

    This was a wear improvement over the 86 models as the longer rod (same stroke) decreased dwell as well as intake bridges to help piston wear.

    -this is where dion was talking about wrist pin height. Honda took up the difference in changing its physical location in the piston. I ran the 86 cylinder with the 87+ crankshaft and a spacer plate. This was not a stroker crank as most think. I did this purely to get more over bores which went up to 69.5 mm or .140" over which came out to 265cc. Not bad with stock parts!

    Again this is apples to oranges but the principles are the same.

  • I am understanding that a greater crank throw will increase the distance the piston travels.

    This increase in travel will cause more wear to a piston/rings and cylinder.

    The longer rod I understand makes for less piston to cylinder side pressure..but still requires the piston to travel a greater distance.

  • Yes Terry Preston no matter how you go about it, If you increase stroke you will increase swept area in the cylinder and cause more wear to the piston, rings and cylinder. Now if the long rod design is used wear will be decreased because of the decreased side forces placed on the piston

  • The Blaster already has a short stroke but also a short rod by design which is why they seem louder then allot of other air cooled two strokes. This is because of the heavy rocking of the piston if nothing but perfect piston/wall clearance. Its why more pistons loose there skirts on the cast pistons that allot of people put in without reconditioning the bore.

  • That is why the long rod is used to reduce the angle of attack to the cylinder wall.