139qmb 44mm BBK with A9 cam and maybe an exhaust upgrade?

[ratdog]

Since my posts about the “A9” cam, I have done a lot of measuring. Biggest surprise is that NONE of the 5 after market cams I have measured have as long of duration as the stock cam. Seems very odd, but when I got my first results, I decided something must have gone wrong and shortlly after the battery died in my indicator. So with fresh battery in place I redid the measurements and was able to include a number of other “A9” cams. First, I was surprised that A9 cams are not all the same, and none of them have more duration or more lift then stock. In fact a number had slightly less lift. I measured a couple taking readings every “hard tooth” ( a couch over 5 degrees). I was hoping to get some one to plot the lift by degrees to give us a “ picture” of the lobes we could over lay. No one was interested in doing that so I just graphed them in my spread sheet so I could see them. The so called preformance came lift the valve laterin the intake cycle!

At any rate, I was very disappointed with what I found

[scooterpimp]

Dont know what the hangup with the ((A-9)) cam thing is ? Seems like those whom actually used them recieved some gains..im droppin one in my current bbk build. Im no machinist , but my eyeballs & old school calipers seem to show wider lobe tip/ duration on the a-9 i have over the 2 stockers i had on my shelf.maybe there are a pile of knockoff a-9's like many other so called performance items out there???

[ratdog]

Well I’m guessing you already read my post on the the A9 cam. And if you did, I list the exact duration and lift on all those cams. If you want, give me an email address and I’ll send you the spread sheet that showes the lift for every 5 . 2 degrees movement.

If you haven’t already removed your stock cam, do this. Take off the valve cover and the flywheel cover. Take out the plug to make this easier. Now move the flywheel until you find where the intake valve first start to move. We are interested in Valve movement, not rocker arm movement. Now draw a line with a sharpie from the center to a point outside the fly wheel. The ignition trigger might be the easiest. Then rotatable the flywheel until the vale is closed, draw another line

When you install the A9 cam, do the same thing. Unless you have a very different A9 cam then the 5 I have, you will find the A9 cam opens later and has less duration.

The A9 cams I have tested are what I call torque cams. Pure guess, but I believe they made them to give more torque but keep the power peak at the same 7500 RPM the stock cam is tuned for.

If you have a dial indicator, set it up to measure the valve movement. I,m willing to bet that you will have no more then .183” of movement whiny what ever cam you measure.

[ratdog]

You know, if you want to put in a little extra time, you could find some great info on this deal. A lot of people (including myself) have reported an increase in preformance with the A9 cam. Problem is, most don’t do JUST the cam, and I haven’t seen anyone that actuly did before and after test results.

Now the numbers indicate that the A9 is a torque grind. More torque should produce better pick up. It does not , however mean more power. On these bikes that should be indicated by higher RPM and higher top speed.

All three engines I have worked on ( well I guess it should be 3 out of 4 if you include the paper boy’s bike) have “ A9 cams. But both Red bike and Black bike got the new cam with the BBK. Now blue bike got just the the cam. And Ed said he could feel more power when taking off. He also said he was getting 1.5 more MPH after the cam. Well the cam was the only major change we made, but we did also change the plug and changed from 10w 40 petroleum based oil to 20w 50 synthetic oil. I would not expect the oil and plug to make a measurable change in preformance. So I have been telling people we got another 1.5 mph because of the cam. But we really didn’t do before and after testing.

I think it would be great if you could do that testing! I’m thinking make several 0 to 30 timed runs. And maybe a top speed after 1/2 mile run. Then after installing the cam and setting the lash, do the same tests with with the “ after cam”

I would expect quicker 0-30 times because the cam is a torque cam. But if your top speed comes at , say over 8500 RPM, you might not get much change in top speed.

If you have a compression gauge, it would be fantastic if you could do a warm engine compression check before swap, and another after the swap. Logic tells ud that a preformance cam has more duration, and therefore could lower the compression a little. The measurements I have taken on the cam, don’t show greater duration, or earlier opening, and I would guess that you don’t see any real loss.

Looking back, I wish I had done this, but at the time I had no reason to think the A9 DIDN’T have greater duration.

In honesty, it really dosent matter because I think everyone gets better 0-30 times, and that a good thing. But if one thinks they have to increase compression to compensate for the “ hotter” cam, that my not be accurate. If one is already running super high compression, and a very hot engine, and hopes to cool the engine off a bit with a hotter cam, that could be a very bad thing.

I’d love to see it, but that’s a lot of work for nothing.

I would very highly recommend you do some plug chops to see wher your mixture is before you put a lot of miles on it.

[KSR Moto]

I have everything from this topic except A9 cam, runs great and top speed is around 43mph

[scooterpimp]

Ok , im just gonna drop the cam in & ride, lifes too short to hold a 3 day class on a pencil eraser.

[ratdog]

dumbahihi22

The three engines I have put these cams in, all run great. But they may not be running better then if they had stock cams.To many of us, the $30 to put in one of these is no big deal, so its sorta a "what the heck" deal. But there are some that read these posts that don't do their own work, and having a cam changed by a professional could be very expensive.

To me, it has become a bit like swamping out the CDI box and coil. The experience I have had with this is that it is a total waste of money. The after market CDI boxes I have had contact with, no longer adjust the the advance. they are at full advance all the time and the only effect I have seen is that they make the bike harder to start. Same goes for the after market coils. the ones I have had contact with will not jump as large a gap as the stock coils.

As a result, I and many others, tell people not to waste their hard earned money on these parts. (Black bike now has a CDI that you can program the advance for every 1000 rpm change. but that is a $200 box)

I have read a lot of posts where the posters are asking where they can get specs on the after market cams. I measured 5 different cams. I posted the results of those measurements. I even measured how much lift the cams have at TDC on the intake stroke. A lot of posters have worried that changing pistons will have their valves running into the piston, so I think that is a good bit of info.

If not anything else, at least the measurements I took show that not all "A9" cams are the same. before measuring, I thought that an A9 cam from one place would be the same as a A9 from someone else. I come from a world where if you buy a "B" exhaust cam for a 88, its the same exact grind no matter who's name is on the box. Now we know in the Chinese scooter world, the "A9" grind is not the same grind from one cam grinder to the next. To me, that is both important and disappointing.

[ratdog]

Scooterpimp, I was just sitting here thinking, and of course your “A9” cam is different! I have not found two brands that were the same yet! So you mentioned you used your old school calipers to measure, what did you get for the cam circle on the intake!? And the max lift? Was the exaust the same? What brand name is on your cam? You may have found the best “A9” cam yet, and I think a lot of people would benefit from that knowledge. I’m sorry man, I just wasn’t thinking that with all the differences i’ve Seen, there could be one that is better then stock

[scooterpimp]

Wow , relax. These are only chinese scooters. Box says Naraku v2   , it said recomended for 47mm + bbk. .

[benficacm]

Just a quick update. I had to bump the slider weights up to 5.5 gram. I was pushing 8500-9500 rpm. Had to de-tune to get it in the 7500-8500 range. Im 225lbs if that helps any other people out. I’m really digging this taotao thunder. The 12 inch wheels and dual rear suspension is super comfortable. I tried out another taotao with smaller wheels and single suspension and there is a noticeable difference in ride.

[scooterpimp]

Im a fan of 12" wheels & twin rear shocks myself..more stable imo.

[ratdog]

When testing red bike (Ice bear with 10" wheels) My son got it upto 53 MPH and suddenly slowed to 40. When he stopped, I asked what went wrong, and he told me it was very uncomfortable running this thing at over 50! (note he normally rides a 250)

[KSR Moto]

Sept 12, 2018 3:44:55 GMT -5 ratdog said:

When testing red bike (Ice bear with 10" wheels) My son got it upto 53 MPH and suddenly slowed to 40. When he stopped, I asked what went wrong, and he told me it was very uncomfortable running this thing at over 50! (note he normally rides a 250)

I agree but it depends, I feel more comfortable on 10" than on my 12" although it should be opposite, for high speeds you need balanced tires, good shocks etc..

[ratdog]

Our road has some dips where the pavement has sunk a bit. It has been blacktoped over, so you don’t notice it. When you hit that little dip at 50 mph on one of these little guys with the 10” tires and what is most likely the cheapest shocks they can spec, it is a real fun time (G). He’s only about 160, but the bike still bottomed out!

[GrumpyUnk]

Somewhere around here I noted that one of the vendors was selling final drive gears that would not fit. The diameter was 1-2mm larger than the OEM. It took some arguing and pictures of the micrometer on the original gear and their product, and conversation with their 'tech' in China before they admitted it was out of spec and ordered a replacement.
I suggested they check their whole stock for proper diameter... and the product was pulled from their site. I also suggested pictures with dimensions of diameter, etc, which they later did.
If a vendor is able to sell a gear that won't fit into the gearbox and mesh with OEM gears, or THEIR OWN gears(suggested I buy a full set, which I had already done), and get it by the retailer/wholesaler inspection, I would bet that cam grinds are all over the place from here to Alaska. FIWIW. It would not surprise me in the least that the grinds differed, perhaps even cam-to-cam from the same vendor, but that's going a bit far.
tom