KC Powersports KC70cc HELP

[TopCatGr58]

Hey there folks,

A neighbor kid got a PepBoys...aka...KC PowersportsUSA.com 70cc mini dirt bike for Xmas. IT didn't come with a tach, and he apparently redlined it, and stuck a valve! I have agreed to try to help him work on it, have found from the PepBoys site, a parts fiche and #'s catalog.

The KCPowersportsUSA.com site doesn't work. It has a single cam with adjustable rocker arms for the valves. There is a large round chrome cover over the timing chain in the head, but I can't see how it comes apart/off?!

IS anybody familiar with this machine? Anybody know where I can find some basic info, like torque specs, timing specs for the cam/crank.

TIA!
T.C.

[prometheus578]

"Cloning"

These things, like stuff from Sundiro, United Motors, Hyosung, etc, are just copies of Hondas, etc, made under license in South Korea, Taiwan, Singapore...
Post a pic of each side o' the engine and let's see if we can match it up.

[TopCatGr58]

Hey GNEPIG,

Thanks for the info, will be looking for your reply.

Hey Prom,

They have a parts file PDF so can't easily post a photo, but you can follow this link, and you will be able to see the parts fiche in PDF format:
http://www.pepboys.com/transportatio...arts/06027.pdf .

It will be good IF I can order the parts from Honda, cause I went to Pep Boys, and they said "DUH", we just sell them, we don't service them!?!?
T.C.

[TopCatGr58]

BTW,

It doesn't use a battery, just a magneto. So...was wondering HOW and what kind of tach could I try to find to put on it?? I don't think it has any port for screwing in a mechanical cable for that kind of tach, and not sure how or IF I could hook up an electronic one? It's got to have a coil, and I guess the magneto provides the power for the coil, so there must be a low voltage trigger signal coming from somewhere to fire the coil? But there might not be an extra power lead to run the tach's power??

I just can't believe they sould sell these things without a tach, what do they think they are......Harleys!
T.C.

[GNEPIG]

.. here ya go TC, the pic is self explanatory
loosen the bolt on the right side of the head a little bit then tap on it to loosen the cap on the right
.. as far as the tach option, these little bikes are made pretty cheap. i would'nt trust a tach on one of these any more than i trust the speedos. although the R1 pocket bike is the fastest pocket i own, the speedo states i'm going 60 mph ... i dont think so.. the best way to keep the rpm's down is to put in a throttle stop bolt at the grip or a stopper on top of the carb slider.
.. if you need any more pics let me know

[TopCatGr58]

Input, need more Input!

Hey GNEPIG,

That's awesome! I also see some torque specs on a few of the bolts, the side head bolt, and the cam sprocket bolts, but NOT the head cap bolts? Also, do you have a page that shows the cam and crankshaft timing marks and process for properly timing the cam/crank?!

With that, I should be able tear this thing down and get it fixed pronto! Yeah, a throttle stop sounds like the right idea, thanks!
T.C.

[LoserShoes]

Does it have a kill switch? Might be enough signal there to drive a tach.

Steve

[GNEPIG]

.. ok page 17-5 is updated with the head nut torque specs.
this book is old, i might be missing a few pages and this book is very vague, it is a factory manual not very shadetree freindly.
hope this helps

[Geezer]

Don't know why you'd want a tach on such a beastie. Honda didn't put tachs on most of their under 100cc bikes and then only on a few.

Anyway I'd look for a greared cable drive off the cam. It'll take some looking to find one that you can adapt then you could use a 4:1 ratio tach.

BTW, that parts diagram sure looks familier. I rebuilt dozens of those as a Honda mechanic. I'm sure glad most of the shops I worked at carried Yamaha too. Back then there were precious few Hondas worth having.

Geezer

[TopCatGr58]

Oh my aching head!

Hey Geezer,

I was mostly thinking of a way to try to help prevent the recurrence of the problem it has now, by allowing the kid to know how fast he can and can't rev the engine past!!

Thanks to GNEPIG's diagrams and such, I have gotten the head off. Not a pretty site The intake valve has a nice "S" curve shape to the stem! The valve guide has 2 pieces broken off of the bottom/piston side. The stem keepers pulled thru the spring cap, and I think the rocker arm shaft is also slightly bent.

I just reviewed a thread about removing and replacing the valve guide. I don't have a shoulder punch, not sure what it looks like? With the bottom of the guide partially broken off, Im not sure what I would put the punch against to drive it up/out? It's a little difficult to tell how big the bottom of the guide is, or where the guide ends and the head begins?

Would I need to try to use some sort of slide hammer device to "PULL" the guide out vs. driving it out from beneath!? I have read that I need to heat up the head to a few hundred degrees in the OVEN!

I'll be stopping by the Honda shop to order the required replacement parts,
Intake Valve,
Valve Guide,
Spring Keeper/cap,
Guide O-ring,
Valve Seal.

BTW, the piston has a mild DENT in the top of it where it hit the valve, but no actual hole! Not much compared to the recess that is forged in the top for the valve clearance! There are no scores on the cylinder wall, so the piston appears okay!
Thanks again, for your help!
T.C.

[Geezer]

I tried to fix the spelling and grammer problems as well as add a few more technical bits but it wouldn't let me edit my post, so here goes again.
---------------------------------------------------

Heat the head to 350 degrees F and the old guide should almost fall out. To install the new guide, leave it in a deep freezer over night and it should just about drop into the hot head.

From the sounds of it, that cylinder head my not be worth fixing. If the rocker pin is bent, the aluminum in the head is likely damaged beyond repair.

I used to work at a brand K dealer ship and a local store gave away a small quad in a drawing. The kids in the family kept bending the intake valves because they didn't bother shifting. The owner of the shop managed to get it covered under warranty both times but we knew the third time wouldn't fly.

I shimmed up the valve springs until they were a little short of binding at full lift so that the springs will bind just before the valve kisses the piston. Then I worked over the rocker arms to remove dead weight. If you can find a copy of the Phil Irving book "Tuning for Speed" or his later book "Restoring and Tuning Classic Motorcycles" he does an excellent job covering this work. Anyway the valves didn't bend again but I was always afraid they would rev it till it tossed the con-rod.

A tach won't help a twit that's too stupid to shift. Some proper instruction and the threat of a good swift kick in the ass if he blows it again might help.

Geezer

[trbig]

Ya hear that TC?? Geezer wants you kick his a@@ TWICE!!



Tod

[Geezer]

The damn system wouldn't let me edit my post to fix the grammer and add a few things but yes, kick his stupid butt twice.

Geezer

[GNEPIG]

.. i dont think twice will work, three times has always worked for me
triple clean those carbs
triple kick that butt

[Geezer]

Originally posted by GNEPIG
.. i dont think twice will work, three times has always worked for me
triple clean those carbs
triple kick that butt

What ever it takes...

Geezer