Evolution of a Baja

M

MJL

Active Member
#1
#1
I've started several threads related to my Baja, so I thought I'd put them all in once place and keep everything here going forward for better reading. I couldn't really call it a build, as I am not building much of anything, more a series of incremental improvements, thus an evolution.
 
M

MJL

Active Member
#2
#2
From 1/23/18

Worked on the Baja a fair bit today. Changed the oil, pulled the clutch to measure the shaft just to be sure, went ahead and cleaned the clutch and oiled the bushing while I had it off, replaced the missing master link on the short chain, lubed the chain, and adjusted the throttle cable to get it to open all the way. I don't think the previous owner ever had full throttle! Although, they really didn't need is as all they did was make laps around a 1/4 acre lot. Went ahead and threw in a 140 tube with the stock jet. Hit a road block though when I couldn't get the brake adjusted. I pulled the rear drum to inspect and found separated brake lining. Ordered a cheapie set of shoes off of Amazon to get it going, but also ordered the Honda shoes off of e-bay.

I did put everything back together enough for a little test ride around the yard. Can't compare performance fairly to the 200 EX as they are geared differently, but while strong, the engine certainly doesn't seem to have the thump of the lightly modded 200 EX (yet!). While similar to the Coleman at first glance, the Baja is quite a bit different design. The riding position and handlebars are much more upright resulting in a very different feel. I haven't measured, but the wheelbase might be a touch longer on the Baja as well. Once I get the brake shoes on, I'll do a top speed run just to see what it can do with the stock setup, but that won't last long as I have torque converter (OldMiniBikes), spare belt, and proper lug nut ordered;)

Lug nut source
https://www.oldminibikes.com/forum/...ap-lug-nut-torque-converter-installation.html
 
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M

MJL

Active Member
#5
#5
Got my parts orders in mid week, but just got a chance to mess with them today. Swapped out the 10 tooth TAV sprocket for a 9. Acceleration might have improved a bit, but hard to tell just ripping up and down the driveway. It's too wet/icy for the 600 ft speed test. They sent me the wrong rear sprocket. I ended up with a #80 30 tooth instead of a #41 70 tooth. Talk about a chunk! It would look pretty wild on a mini bike! So back to the mothership with that one, hopefully the next one will be right. I'm predicting huge effect from the 70 tooth. Played with the TAV garter springs a bit today. While noticeably stiffer, the comet springs are also around 1/2 inch longer than the clone springs. I put the white springs on and can't say I notice that much difference. I really need a tach to dial in the TAV. Maybe I will put that on the list. Other improvements include drilling the jet to .32, and throating the muffler. Pics are from the 200EX throating, but procedure was the same.

image.jpeg
image.jpeg
 
M

MJL

Active Member
#6
#6
Rode around some more with the white garter springs (3100 rpm engagement) and I can definitely tell a difference. Takes a bit more throttle to get started, but when she goes, she goes! Crack the throttle too fast and the front wheel will certainly come off the ground. I was able to pop a wheelie even while leaning over the handle bars. It certainly launches harder, but with a bit of a jerk, so I don't know if I'll keep them on or not. Just have to wait and see how it is after the 70 tooth sprocket. Speaking of the sprocket, I think I will need to come up with an idler setup of some sort to keep the chain off of the frame, but I'll cross that bridge when I come to it. I did get the flywheel lapped and 6 degree key installed. Might just me, but I think it sounds a bit meaner. I've polled the audience in this thread...

https://www.oldminibikes.com/forum/...-advance-change-engine-sound.html#post1161159
 
M

MJL

Active Member
#7
#7
Looks like I still can't post video links, but there is a very short one of a Coleman CT200 with a TAV and a 71 tooth sprocket doing a little hill climb. Looks interesting. Search for "Coleman 200 71 tooth" if you are interested.
 
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Raskin

Raskin

#8
#8
71t with the tav should be a torque monster for sure..the way I post vids off you tube is to right click copy and paste here.
 
M

MJL

Active Member
#11
#11
Thanks Fomogo!

I put the yellow driven spring in today. Using my bench vice as a clamp, I was able to put it in the "strongest" hole without too much trouble. I am pleased with the results. Not exactly sure why, but the engagement smoothed out, settling down the launch wheelies and making it more drivable, which is probably a good thing! I made a 200 yard run with the cover off just to see what was happening. The TAV never made it into overdrive, which is fine by me, as I don't need any more speed. It seems to be running right in the middle of the power band and will easily climb any hill I care to climb, but I still can't seem to get the little jumps I enjoy so much with the 200 EX with a 60. tooth rear sprocket and stock clutch.

I was looking a bit closer at the chain clearance I will need for the 70 tooth rear sprocket, and I think I might be able to use some washers to lift the rear of the engine a 1/2" or so. Not sure if it will get me there or not, but I figure it is worth a try before messing with a tensioner.
 
M

MJL

Active Member
#13
#13
Just packaged up the second wrong sprocket to go back to Amazon. Found a 72 tooth for a few more bucks and convinced them to overnight it to me for free given the two previous mistakes. Fingers crossed...
 
M

MJL

Active Member
#14
#14
Ugh, Amazon just e-mailed to tell me they didn't have the sprocket they said they had. So no sprocket today. I ordered one from an industrial supplier. We'll see if that works...
 
M

MJL

Active Member
#16
#16
Finally got my 70 tooth sprocket in! Only took 4 tries! Spent the afternoon opening up the bore, drilling mounting holes, and raising the rear of the engine 3/4" to get the chain to clear. First test ride, it was obvious the driven pulley wasn't upshifting enough with the yellow spring in the tightest hole, so I switched it to the first hole. Much better.

Overall I'd say I like the performance better than the 50 tooth, it certainly gets up to speed faster, but it is still not pulling as hard as I think it should off the line. Could be my belt is slipping. I have another to try when I get a chance.
 
M

MJL

Active Member
#17
#17
I tried the tighter belt and it might have been a touch better, but it's so tight it won't idle, so I went back to the previous one. Worked the bike out hard today on the few little trails we have and plenty of full throttle 200 yard sprints. When the kids got home, we fired up the 200EX and had a big time in the field with 25+ races. Obviously, I was able to beat the throttle limited 200EX every time, so we worked out the lead time needed for a close finish. Interestingly enough, they both came off the line about the same, although the EX was hauling 100+lbs less. The TAV equipped Baja didn't really pull ahead until the EX topped out. Never smoked the belt despite all the hard launches, it actually seemed to hook up better as time went by, not sure if wore in, or just got sticky from the heat!

Couldn't help myself ordering a 7 inch driven pulley and belt, just to see what it was like. I'd still like some rooster tails!
 
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