Some ZS167FML questions for racing sidecar

[humanbeing]

Programmable http://item.taobao.com/item.htm?id=3289740994
It runs on DC just like those Suzuki , so u need another suitable coil like this http://www.sanxin.com.cn/Exhibit/exhview.asp?pid=62 (stock: http://www.sanxin.com.cn/Exhibit/exhview.asp?pid=55) + a reliable rec/reg that supplies DC power
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#17 The "developer" of that product tells the truth on ***REAL*** racing "curves"
http://www.motoyes.net/bbs/forum.php...&extra=&page=2

[Jibberwobble]

Originally Posted by Weldangrind

Brilliant box! It should certainly keep the electrical bits cool.

Thanks, it was only a quick knock up and would have put nice radius corners on it if I had time.

Originally Posted by Wild_Alaskan

looks like a very interesting racing series!

Yes this is our first year at it, been racing the minibikes four a few years now and the sidecars have always looked interesting. After a year or two of wanting a go I finally got my s**t together and aquired this old girl, then promptly chopped it up to make it 'less bad'. We are having a ball, the racing is very close and the team work side of things is very rewarding.

Originally Posted by humanbeing

Programmable http://item.taobao.com/item.htm?id=3289740994
It runs on DC just like those Suzuki , so u need another suitable coil like this http://www.sanxin.com.cn/Exhibit/exhview.asp?pid=62 (stock: http://www.sanxin.com.cn/Exhibit/exhview.asp?pid=55) + a reliable rec/reg that supplies DC power
---
#17 The "developer" of that product tells the truth on ***REAL*** racing "curves"
http://www.motoyes.net/bbs/forum.php...&extra=&page=2

Thank you Humanbeing. I am however having considerable trouble understanding the translated version of these pages and how I would go about purchasing the required items. I will go investigate some more........


Ran the engine again with the power jet pipe disconnected and it's exactly the same as before. Didnt have time to try different jetting due to being up to my pits in sticky goo bodging up the bodywork for one last battering. New proper bodywork coming over the winter.

[Jibberwobble]

Some nicer CF parts made for minibikes, 2x huggers, chain guard and custonm bodywork.

[Jibberwobble]

Well after a nice long w/e in Wales we had two days of sun and one day of wind and rain on race day.

The long manifold was causing problems in that it was creating this back flow thing and belching out a huge cloud of vapour that was soaking my arm and cleaning/dissolving Chads visor when he was out for the right handers! first thing was to rule out jetting and the new lower altitude in relation to the tank so we ran it with the fuel turned off and let it empty the float bowl. Even when it was starting to pick up revs at tick over due to getting lean on an empty bowl it still pumped out the plume when the throttle was twisted.

I used the top half of the manifold which is similar in shape to the old blue silicone tube elbow that was on there before and remounted the carb in it's previous position. The belching cloud was gone and we no longer had a racing tricycle steam train. So I can only imagine that the large volume manifold was storing some higher pressure mixture which then backflowed after the intake valve shut and then back flowed out of the carb picking up a second dose of fuel as it passed the tube. Some research needed me thinks.

It was running nice after remounting the carb and quali was looming so we left it be after that. Qualified 3rd which is our best yet and knocked 0.6 sec off our previous best lap time at this circuit with a 58.6 second lap on a 3/4ish mile track.

First start went well... up to second then nearing the end of the race laying in 3rd we broke the chair wheel axle and spun off. Second start went well with a similar result but we were on the wrong tyres and dropped back to 4th at the finish. Last race, did not start, we suffered a split chair wheel tyre and only noticed it on the way to the holding area :(

The zonger is pulling well against the other more modern engines, think it's still the slowest out there but not by much. Our outfit is the heaviest at 110kgs too but we arent exactly total fatties so we end up in the middle somewhere when you look at combined weight.

Going to give her a little run at an indoor track this w/e and may try that other carb. We will then look at what the next step is with the motor for some winter modifications.

[Weldangrind]

Originally Posted by Jibberwobble

...we arent exactly total fatties

Quote of the day!

Interesting plume theory. It never occurred to me that the venturi effect would work in reverse.

[katoranger]

So the next performance improvement will be diets.

[Jibberwobble]

Originally Posted by Weldangrind

Quote of the day!

Interesting plume theory. It never occurred to me that the venturi effect would work in reverse.

The backflow thing happens with two strokes sometimes, when the piston is on the down stroke and compressing the contents of the crank case some mixture escapes before the reeds shut (or the reeds could be damaged) and if it passes the tube at speed it pulls more fuel out then gets sucked back in to the carb mouth for the next indunction cycle and helps its self to more fuel. This really screws carburation. I think boost bottles help sort this out a bit but to be honest I'm not an expert.

The thing I dont understand is why it's happening on a four stroke other than my complete guess above. The carb has had moments of doing this before too even with the short manifold. Leaky inlet valve maybe?

Didnt get to run it this w/e, our track day got cancelled!

Right where's that chocolate pie??

[Weldangrind]

Originally Posted by Jibberwobble

The thing I dont understand is why it's happening on a four stroke other than my complete guess above. The carb has had moments of doing this before too even with the short manifold. Leaky inlet valve maby?

I'm thinking that the reversion is caused by the cam lobe profile, although there's only one valve in the pushrod motor. In a performance four stroke application, it's common to have some valve overlap that helps to fill the cylinder at high rpm. At low rpm, the result is reversion.

Not sure of that can happen with only one valve that is shared between intake and exhaust, but it's fun to theorize about over a pint.

[Wild_Alaskan]

There is a one valve four stroke? Are you sure, i really cant see any way this would work without a reed cage type setup in the intake. My pushrod lifan motor had two valves, A high performance four stroke can have 4 or even 5 valves on a single cylinder. If the timing is wrong (to advanced) then it can spit and exhaust pulse out the intake at low rpms pushing some fresh mixture back with it.

[Weldangrind]

Sorry, I meant to say one cam lobe for two valves. Hopefully that will make more sense.

[Jibberwobble]

Hello there, been three months since I did any work on the sidecar, we've just been messing around on it since the season ended. Must get back on it soon or it will be another **** fight like last year.

Still got all these issues to solve but havent worked out a plan of attack yet. Chassis mods aside I feel a minor engine strip would be beneficial, really want to get the carb out the way so really should make sure everything is ok on the engine before doing more manifold and jetting experiments. Valve seating, cam condition/profile, heavier valve springs or what ever I can find on improving one of these motors.

Got another idea in the pipeline for a second outfit too.........

[Weldangrind]

I'd be shy about heavier valve springs, lest you should wipe out the cam lobe. Instead, try a fresh set of springs and use two shims instead on one. Stuff like that is pennies on Taobao.

[Jibberwobble]

Thank you that's just the sort of information I need

[Jibberwobble]

Originally Posted by humanbeing

Programmable http://item.taobao.com/item.htm?id=3289740994
It runs on DC just like those Suzuki , so u need another suitable coil like this http://www.sanxin.com.cn/Exhibit/exhview.asp?pid=62 (stock: http://www.sanxin.com.cn/Exhibit/exhview.asp?pid=55) + a reliable rec/reg that supplies DC power
---
#17 The "developer" of that product tells the truth on ***REAL*** racing "curves"
http://www.motoyes.net/bbs/forum.php...&extra=&page=2

OK so I'm now doing a rebuild on the outfit, changing almost everything and would like to see if we can make this engine go a bit faster too. I have now acquired the above CDI using tbtrends which was a refreshingly simple exercise in the end.

Humanbeing talks of DC coil and rec/reg

So I now need to get a DC coil which seems reasonably straight forward but what about the regulator, Arent these AC to DC units anyway? (please excuse my ignorance)

Anything else I need to change??

[Weldangrind]

If you currently have a 67mm bore, you need this: http://item.taobao.com/item.htm?spm=...id=13243492906