How big is too big??

[jbthumper]

Yes,i'm talking about the big bore kit for the 125...
I know that there's a 150 wiseco kit....but is there any other bigger kit that can be installed..???

And to anyone who had installed a big bore kit....does it effect reliability in terms of long distance riding??

Thanks
Cheers,

Din.

[phlat65]

the sales manager at Seattle Honda has a 150 kitted sm, with the M4 mini pipe. very cool!! he talked to the tuner that preps the 125 race bikes in germany (I don't know who) and was told the Bottom end can handle 250cc's with out failure.

start with the 150, exhaust, and the ignition re-mapping/ rev increase ( I think they bump it up to 13,000 or 13,500).

[jbthumper]

may i know what do u mean by "bottom end"....is it revving at low rpm for a long time or some sort??

[phlat65]

Bottom end = Crankshaft, trans,

top end = piston, cylinder, head...

[jbthumper]

Wow....!!!!
So if i do put a 250 piston(which i think i won't...don't think it's legal), i would only work on the top end...right??(just for info)


I have another question.....does the 150 kit increase the sm's top speed??
and how much, roughly, does it cost for the 150 kit and all??

[phlat65]

I don't know the cost, I think it is pretty cheap though. yes it will give you more top speed if you gear it diff.

[jbthumper]

[phlat65]

you have put 37,000 kilometers on the 125? what problems have you had?

[jbthumper]

The biggest job i had to do was replacing the water-pump because it was leaking...i didn't check my coolant before i went for a 5 hour ride(only stopped for food and gas... no more than 20 minutes each)..........wrong move..... there were also other stuff like clutch cable and battery,u know. But now everythings ok....apart from that there's nothing else
however there is this wierd noise which sounds like a chain rattling when i rev on neutral...i can't figure out what it is....

[keithcross]

This rattling sounds like the cam chain rattling. Check the adjustment, if it automatic you might need to fit a new chain and tensioner blades. I am not familier with this model, but usually this can be dine without stripping the bottom end of the engine as a soft link is fitted to the chain.

Keith

[DAVID THOMPSON]

hello

37,000 km = 22940miles

its way past time to check or replace at least the guides and
check the chain
mine only has 8200 miles on it and it is getting looked at this winter

doooooo check the guides and chain now befor you break something
or the chain jumps off

also check the cam sprockets for wear
this is one tuff little motor but at the rpm it runs it needs
checked about every 10,000 miles
at your miles i think you will need new plastic chain guides

as for a big bore kit wait till top end jug and piston are trash then do the big bore kit
i have a parts book and shop manual if you need part numbers
or info
ar dave 8200 miles in 2 years tested and approve by this rider
510 miles this weekend on my yearly road trip to a rally in pa

as for max size in cc i heard that over about 180 was to much cost for the power gained ie too much work in a machine shop to make it all fit

[jbthumper]

Hey guys,

I guess i should do a check up on my cam and cam chain then.
My drive chain sliders are ok,though they wear out quick if not properly lubed. I think my external parts are ok because i do my check-up quite often...
I'm going to use my piston to the last stroke . Then i'll use the big bore kit.
Thanks everyone. I'll where to go when i need help now

Cheers.

Din.

[jbthumper]

Hey guys,
does anyone know if the same pin and con-rod can be used for a piston bigger than the 150cc piston??

Much appreciated.

[phlat65]

I don't know for sure, but would say yes. unless you increase the stroke too, then a different length connecting rod may be necessary..

[bdalameda]

I have two 125's - one with the 150 Kit. If you look at the cylinder mods made with the kit you will see that the cylinder was completely bore out larger and a spacer put in between the new larger sleeve and barrel. Even with the 150 kit there is very little area for the head gaket to seal. The area is reduced by about 50% from the stock cylinder. The water jacket around the sleeve has also been reduced significantly. I can honestly say that 150 cc is about as big as practical without a complete redesign of the cylinder and head as well as machining out the cases to accept a larger sleeve. There is also a question of crank balance as the piston is enlarged. This is somewhat overcome in the 150 Kit as it has a thin wall forged piston and a very thin walled lightweight wrist pin to compensate for the higher weight of the larger piston. Can it be done? Yes - if you want to design a cylinder and head from scratch and re balance the lower end.

By the way the 150 kit is a huge improvement over stock. With acleaned up intake ports and a DMC exhaust and unrestricting the airbox the thing runs as good as many 250 cc 4-stroke singles. Also retime the intake cam advanced about 3 degrees help with the mid range and ability to pull tall hills in 6th. Rejetting is a must.