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Discussion Starter #1
Looks like you will need aftermarket rear sets if you were to swap the stock Wave motor with a traditional Honda performance engine because of the kick starter.

So lets assume you are using a big bore kit and a race head with lopey cam and stiff valve springs with the stock lower end - I doubt the stock starter motor would even turn it over without some sort of compression relief. I wonder if you could use a smaller pinion on the starter or if there is even a way to move the starter closer to the flywheel if you could......

Thoughts?
 

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Well wouldn't a more aggressive cam actually lessen your cranking compression?

Im also curious about a compression bump and how the factory starter would handle it, standard is 8:1 or 9:1? I'd like to get it to 11-12:1.. With heads being only 75$ new it might be worth buying one and shaving the hell out of it just to see how it does

Also I'm going to hope honda over engineered the starter and it'll handle high comp, a ruckus uses the stator/fly to spin the engine the engine, they still prove useful at 12:1 so who knows
 

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years ago I build a custom Harley with a high comp, big bore, stroke and big cam. The starter would just barely get it cranking, especially when it was warm. They make manual compression release buttons for Harleys. Drill and tap a hole in the head and the screw the compression release into the head. Before you go to start the bike, push in on the release. It allowed the engine to turn over one a full revolution (i think) before the combustion in the chamber forces the release closed. So that is how they work in theory. I bought my current Harley and sold the other one before I actually tried those.
 

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Discussion Starter #4
years ago I build a custom Harley with a high comp, big bore, stroke and big cam. The starter would just barely get it cranking, especially when it was warm. They make manual compression release buttons for Harleys. Drill and tap a hole in the head and the screw the compression release into the head. Before you go to start the bike, push in on the release. It allowed the engine to turn over one a full revolution (i think) before the combustion in the chamber forces the release closed. So that is how they work in theory. I bought my current Harley and sold the other one before I actually tried those.
This little doohicky is based on that concept. They work really well but require a special spark plug and have to be seated perfectly. Notice the slot in the side of the threads on the plug - that vents the cylinder to a valve under the the black knob. Here it it shown with the valve closed for running condition (knob out). Push the knob in and the valve opens until the first couple of piston cycles then closes. The valve looks just like a mini engine valve and will pass a leak-down test (I did one) so thereis zero blow by.

On a Z50 it is easy to reach down with your right hand and do this and it keeps you from stripping your starting gears. I had two, one went on the Orangutan when it sold and this one I still have. I don't know if it will fit on the Wave head and I honestly don't really want to use it but eventually I will have a BBK and race head. Luckily, Takegawa is coming out with bore and head kits soon and they have decomp heads on their new head kits.

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Cutting-down the head is a bad idea with these motors, more downsides than anything else. You may run into cam chain tension and valve clearance problems. Just as bad, if not worse, combustion chamber efficiency can be seriously degraded. Mo`better, from just about every angle, to source a race head that has the desired improvements...and plays nicely with stock deck height.

Considering what's happening with pump gas, idk if 12:1 will be viable and, if so, for how long in road applications. If you're strictly racing, or can deal with the short leash of high-octane race fuel, then CR is a non-issue. E85 might be a good compromise, but with its own set of challenges - including new/compatible fuel system hardware and ECU re-mapping.
 

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Cutting-down the head is a bad idea with these motors, more downsides than anything else. You may run into cam chain tension and valve clearance problems. Just as bad, if not worse, combustion chamber efficiency can be seriously degraded. Mo`better, from just about every angle, to source a race head that has the desired improvements...and plays nicely with stock deck height.

Considering what's happening with pump gas, idk if 12:1 will be viable and, if so, for how long in road applications. If you're strictly racing, or can deal with the short leash of high-octane race fuel, then CR is a non-issue. E85 might be a good compromise, but with its own set of challenges- including new/compatible fuel system hardware and ECU re-mapping.
Keep in mind me shaving a head will be solely for the fun of experimenting thats why I said at the cost of a new head it'd be worth giving a shot, a friend of mine had his ruckus head shaved .018 and its the fastest (mph) 49cc ruckus that I know of (63mph in open air) it worked out extremely well.. the grom looks to run the same style tchain tensioner as the ruck and if theyre anything alike, installed at full extension will tighten the chain so much the engine won't turn over, so the adjuster can compensate for a lot, shaving .010 or .015 isn't going to interfere with that, as far as valve clearance after or how it will perform with such a shave will only be known once its done and at 75$ for a head, 35$ for a shave and 10$ for a hg.. It's a route I'm willing to at least try
 

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Keep in mind me shaving a head will be solely for the fun of experimenting thats why I said at the cost of a new head it'd be worth giving a shot, a friend of mine had his ruckus head shaved .018 and its the fastest (mph) 49cc ruckus that I know of (63mph in open air) it worked out extremely well.. the grom looks to run the same style tchain tensioner as the ruck and if theyre anything alike, installed at full extension will tighten the chain so much the engine won't turn over, so the adjuster can compensate for a lot, shaving .010 or .015 isn't going to interfere with that, as far as valve clearance after or how it will perform with such a shave will only be known once its done and at 75$ for a head, 35$ for a shave and 10$ for a hg.. It's a route I'm willing to at least try
If the parts diagram is correct, this motor runs the same hydraulic-type, self-adjusting, tensioner assembly as the Wave/Nice engines. I reckon 0.30" of added chain slack won't matter very much. The slightly retarding cam timing may actually help a little at high rpm. And, like you say, $75 is cheap entertainment by current standards.

That said, this motor strikes me as being far more like the Wave/Nice. There's 70mph potential in those engines when taken out to the same displacement as a stock MSX125...via the combination of a high-compression piston, more aggressive bumpstick, & some modest post work done to the stock head. Piston swaps are highly effective, cheap, too - just a thought...
 

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That said, this motor strikes me as being far more like the Wave/Nice. There's 70mph potential in those engines when taken out to the same displacement as a stock MSX125...via the combination of a high-compression piston, more aggressive bumpstick, & some modest post work done to the stock head. Piston swaps are highly effective, cheap, too - just a thought...
I hadn't thought of a "125" piston from a wave kit, could probably pick up a piston alone for 60$ or so and be a "drop in" affair iirc the groms valves are off set to one another, is that typical with these engines?

edit: the wave is the same with the offset valves, a high comp piston from a "125" kit could very well work
 

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I hadn't thought of a "125" piston from a wave kit, could probably pick up a piston alone for 60$ or so and be a "drop in" affair iirc the groms valves are off set to one another, is that typical with these engines?

edit: the wave is the same with the offset valves, a high comp piston from a "125" kit could very well work
I can't give you a specific-application piston. I've tuned various flavors of Nice engines; they start out with a 50mm std bore and can be taken out as far 59mm...if one is sufficiently brave and well-heeled. Still, high-compression pistons are fairly easy to source, even in OEM std size. Takegawa makes a very nice hi-comp 54mm slug, which takes displacement to 127. But, again, Taky parts aren't cheap. Still, the 54 x 55.5 undersquare tune, with "street porting" makes amazing power, across the entire revband (with a guesstimated peak around 13-14hp), even with the small, OE, valves and a semi-arbitrary 9500rpm redline. The stock rotating assembly is downright porkly.

At present, I don't have enough Grom-specific engine knowledge to comment intelligently on the valve layout. Going by what I've seen, so far, in photos, the head design looks like it has improved breathing capability, compared to the old Wave/Nice, and that can only be good. The roller rockers certainly open-up a world of possibilities. With the right springs & lightweight retainers, it should be possible to run nearly "square" cam lobe profiles that have lots of "over-the-nose" lift with relatively short gross duration...ideal for a road bike. Just raising peak hp to ~9000rpm+/- ought to give easy 70mph top speed. IMHO, that'd be a healthy improvement from very little change (parts and, the unintended-but-appropriate monetary reference).

Since this engine series has been sold in SE Asia for some time now, I'd expect outfits like Akunar to have aftermarket pistons in a number of different sizes & flavors...as well as cam choices...for very reasonable money, even with shipping.
 

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Akunar have the parts, waiting for me is a 150 cylinder, bigger throttle bodies and fuel controller from them ;-)
 

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It's of a pcx150, won't be home until Friday so will post pcs then.

According to the parts fische the MSX/Grom throttle body is very different than the PCX, the MSX uses a flange type throttle body vs the PCX which uses a typical clamp/boot style, perhaps the manifolds can be interchanged?
PCX (125/150)



Grom/MSX
 
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