Hello everyone I ordered a BBR stage 4 kit for something to tinker with. I also got a cheap bike to put it on. Roadmaster Granite Peak Mountain Bike 26. I am used to working and porting saws. So before I run this engine im going to tear down and clean everything up. My question for you guys is say a top 10 or 20 list of things to replace from the bike and or engine kit.
New guy first build
- Thread starter James1968
- Start date
Welcome!! What do you mean by "replace"? You can get upgraded parts for many of a standard parts found in most stock kits. For example, most kits come with a standard muffler exhaust pipe but you can get really good expansion exhaust pipes that will really wake these little engines up. Also, lots of people find it easier to get a sprocket adapter for the rear sprocket so that it will drive the rear wheel hub instead of driving the spokes. If you want to go a little faster you can get a smaller tooth rear sprocket or you can get a higher tooth rear sprocket for better hill climbing. Another good upgrade is a high compression head, get one with large fins that helps the engine run cooler as well as give you a better compression and more power. Also, if you are going to clean it up you should port the cylinder.
As far as bike parts go, make sure you have good rims, as fat as possible, the fatter the better, mag wheels or double walled rims are best but not necessary and get fat tires as fat as possible without the chain hitting. Make certain you have good front and rear brakes, disc is preferable for the front but cantilever ones can work fine. Get good tires unless you want to replace them every few weeks.
As far as bike parts go, make sure you have good rims, as fat as possible, the fatter the better, mag wheels or double walled rims are best but not necessary and get fat tires as fat as possible without the chain hitting. Make certain you have good front and rear brakes, disc is preferable for the front but cantilever ones can work fine. Get good tires unless you want to replace them every few weeks.
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Well I’ve got the ports cleaned up. I couldn’t clean the transfers up, my pencil grinder died. I would say the biggest gain was matching the gaskets, and the little banana pipe had half of the exhaust port covered. Question the plating looks to be very thin? Probably a week point to longevity, has anyone had us plating to re plate one of these? They do a excellent job. Send the jug and a piston and they take the old plating off. Do a high quality plating and hone to correct bore size. Also both the stock and the “ stage one performance Cdi look they same. And does anyone know what there performance carb is? Thanks for any knowledge.
Well, it's not really worth it, stock jugs for these things cost less than $20, all these cheap Chinese parts are disposable, but you can get thousands of miles out of one if it is tuned correctly. Make sure you use a good 2 stroke oil, mixed at maybe 24 x 1 for break in and 32 x 1 after.
The stock carb is actually surprisingly good but I found these carbs easier to tune.
https://www.ebay.com/itm/Racing-Car...oke-Motorized-Bike-Bicycle-Parts/302552088822
One thing you want to make sure is when you mount your engine on the frame that you have enough room for the carb, if you don't, you can either adjust your engine or get an off set intake. Also, you might need to rejet to tune the carb properly, usually the stock #70 jet is often too rich. You can either make your own jets or purchase them.
https://www.ebay.com/itm/2-Stroke-M...mm-69mm-70mm/173360980466?hash=item285d1ea1f2
https://www.ebay.com/itm/2-Stroke-M...mm-64mm-65mm/183269111821?hash=item2aabb0b80d
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Does anyone know what the cc is of the BBR high compression head? I got the motor together last night and have 0.031 squish. I didn't have anyway to measure the CC's. But by looking at it the compression may be to high. Also FYI the BBR 4 kit comes with "stage1 CDI" its just a stock CDI with a NGK wire on it.
I'm pretty sure that head is a 6cc one but not positive. A squish gab between .025"-.035" is optimum. Exhaust pipes like this work very well.
https://www.ebay.com/itm/MZ-MOTORIZ...193436?hash=item3f97c4bfdc:g:kVQAAOSw5nFaxoaI
Also, there are some straight pipes that work well too but I can't find a link for them right now.
https://www.ebay.com/itm/MZ-MOTORIZ...193436?hash=item3f97c4bfdc:g:kVQAAOSw5nFaxoaI
Also, there are some straight pipes that work well too but I can't find a link for them right now.
the banana pipe did ok in my experience and the whole time I had a silencer I made out of the stock muffler welded on the end of it to keep it quiet.
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The pipe you got doesn't look like the same one that comes with the BBR Stage 4 kit. That one on your bike at least has a small header, but it's certainly not the same, take a look---> https://www.bikeberry.com/gas-engin...e-engine-kit-stage-i-performance-package.html
Someone once took one and cut it open proving the expansion pipe is useless.
That one you have looks like a true expansion pipe, which one is that?
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I've been going to the Southern California Motor Bicycle races for a couple of years. Of course I don't win but I just go race around the track, BBQ, camp at the track in my RV, and check out the kick'n bikes. Here are 2 examples of what they are doing. These snake pipes are pretty effective expansion pipes, I think this guy got 3rd.
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This bike was probably my favorite bike. He had dual front discs and even had a special hub to use a rear disc brake. His expansion pipe and reed valve set up makes him fly but he has the best rims, tires and fork to handle it. The fork was unbelievable quality, motorcycle quality. I couldn't believe how maxed out this guy's bikes are, yes, he had 2 of them, try not to drool.
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That sounds about right for your set up, although it might be a bit sluggish. How is the engine running, does it 4 stroke at any point on the throttle range? You can get much more low end if you get a better expansion pipe or a reed valve, although the reed valve eats much more gas so you can't go as far on a tank. But it sounds like you are set up pretty good, don't forget to tighten all your screws as the vibrations can unscrew them at the wrong moment. Keep your head nuts at about 15 foot pounds of torque. Also, if you get a slightly smaller tooth rear sprocket, like a 40 tooth, you can get more top end but less acceleration and hill climbing ability. Post a pic!
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I have gps it at 32.9 with the 44 sprocket. I just made the pull from 9 to 30.9 to time the acceleration. It does 4 stroke just a bit. I have thought about the sbp exhaust. But it always seemed to me that dirt bikes with expansion pipes had no power down low.
And thanks for all the tips and tricks!!
And thanks for all the tips and tricks!!
If you get the SBP expansion pipe just make sure you have a long header and you will get more low end. I got one on my first bike build. I still have it on there and I get lots of low end, the header is about 16" long though.
