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Old 09-10-2010, 04:47 PM
azdriver azdriver is offline
Motorized Bicycle Newbie
Join Date: Jun 2010
Location: valley of the sun
Posts: 10
Default Newb's Ross Cruiser build

So i picked up this clean late 70s early 80s (??) Ross 5 speed cruiser bike as the donor for my first motorized bike build. Here she is when I brought her home:

the whitewalls were not my style so i spooned on some mt. bike tires i had in the garage. I also upgraded the brake cables and the pads to koolstops because the brakes were seriously weak. still not great compared to modern stuff but good enough for now. I might upgrade to a fork with v brake bosses later on.

a few days later the motor kit from showed up:

shipping was fast and I was impressed with the overall quality of the kit. I replaced the acorn nuts on the cylinder head with upgraded hardware and I was glad I took the head off- there were some metal shavings sitting on top of the piston! I think they came off the threads of the sparkplus hole. Seems like they just thread it real quick and then pop the plug in there without really taking much care. Just glad I didn't fire it up with the shavings in there. Replaced the scary cheap looking china spark plug (with 4 electrodes!) for a traditional NGK.

heres a look inside the cylinder. not much cross hatching:

I did some light sanding of the cyinder head on a glass table and then coated the head gasket on both sides with permatex spray copper sealant- i've used it with great success on other 2 stroke dirtbikes i've had and figured it couldn't hurt. replaced the header and intake nuts with locking ones also.

The motor went into the frame very easily with only one shim needed on the front. the header was a problem thought and was hitting the pedal. I had to get medievel on it with the bench vise but i eventually got it to jusssttt clear the lef crank.

put the rag join on in my living room (i have an understanding wife):

The rest of the build went pretty smooth, filled 'er up with 18:1 premix and she initially bogged and didn't want to run. In the middle of the street i realized i had the choke full on instead off so i flipped the lever back and tried again. brappppppp, brappppppp, and she started right up! rode it around the block and noticed that the engine stalled even with the clutch disengaged at stops. this problem quickly went away on its own and i noticed that the bike seemed to run better the more miles i put on her. I've put less than 20 on it but so far so good. cruises easily at 20mph with the 44t rear sproket.

Motor is definitely running very rich but that is probably intended for break in purposes. after 200 miles i may lower the needle a notch or two. still need to clean up the wiring some and shorten the throttle and choke cables. I shortened the clutch cable (and housing) which was ridiculously long. The primary cover had grease on the helical cut gears so I just put some locktite on the threads of the screws and called it good.

The engine runs well but seems to come in and out of the powerband, I saw something in another post about "4 stroking"? maybe that is what is happenning. seems like it wants to "get on the pipe" but can't quite get there. Not a major issue but I think there is some untapped potential in this motor that can be realized with a little tuning.

the bike as she sits now:

Last edited by azdriver; 09-10-2010 at 05:17 PM. Reason: added to story
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