Some ZS167FML questions for racing sidecar

[Jibberwobble]

Hi again

Well after a rather longer than expected interlude dealing with life's little obstacles it's time to have a look at the engine in my little sidecar (pushrod CG clone) and see if it will go any better with a bit of tickling!

We have now done three rounds of the British championships with my Zong powered outfit and we are looking quite competitive. There are 10 or 11 outfits in our grid and we run in about forth position usually which I'm pretty pleased with to be honest considering the norm is to get lapped every race for most of the first season.

The engine has run very well so far but is needing a little more power on the straights. The others are running various 80/85cctwo stroke moto-x engines, CB125 bottom ends with 160cc barrels or CRF150 four stroke Moto-x units. We have the least power out of all of them But for some reason I have come to like the Zong and would like to give it a fair crack of the whip before disregarding it as not good enough for the job. If I cant get it up to speed I will consider a different chinese engine before going Jap.

One point that is going to make engine development hard to measure is that the damn thing wont fit on any dyno I've come across yet! One way or the other the zonger needs to be putting out 20+ HP and ideally 22HP would be nice. I'm not sure this is ever going to happen though.

Currently I have a new exhaust going on soon and need to get onto checking the valve clearances before the next round in two weeks. Also got a big list of other mechanical issues to resolve.

So for some questions about these engines.......

I am running a 27mm mikuni, I want to try something bigger but what is too big? I'm thinking either a 30 or 32mm?? also a Carb that is not so tall as the Mikuni would be handy as it currently very in the way and stopping my laying down properly on the outfit. In addition I am considering a custom manifold to get the carb down lower but not sure how long the manifold can be before it starts to effect atomisation and power?

Is the clutch on these engine usually VERY stiff? It's definitely not the cable.

I need to have some gearing options, I am on 17-front and 24-rear (using 11" kart tyres (tires-american)). How big will I get away with on the front? Having an 18 and a 19 would be good but not sure they will fit. Cant find anything bigger than 17t for the Zong so is there a jap engine with the same shaft dimensions so I could buy a quality sprocket or two to fit?

Does anyone have any output figures from one these engines with all the restrictive rubbish removed?

Should I stick with standard Zong CDI's or is there a Honda etc variant that is the same or better?

Same as above for coil?

Anyone messed with valve timing?

[Weldangrind]

So many questions!

Before we begin, what is the actual displacement of your pushrod motor? Are you limited by displacement in your racing class?

This is the carb I like for 200 / 230 China motors: http://www.ebay.com/itm/Carburetor-C...4979d6&vxp=mtr I jet them with a 112 main and 27 slow at sea level for a 200, 115 / 30 for a 230.

This is the intake tube I have on my atv: http://www.ebay.com/itm/30MM-MANIFOL...fb51b8&vxp=mtr Not sure if it costs any power, but I doubt it. The air and fuel are happily sucked uphill by engine vacuum.

The clutch isn't normally that difficult; certainly no more than an average CG125. If you can't find a mechanical problem, perhaps this would help: http://www.ebay.ca/itm/Chrome-Hydrau...4c0632&vxp=mtr

You're using a 17 tooth countershaft sprocket and a 24 tooth rear sprocket? I can't believe that little motor can use such tall gearing. I figured that 40 teeth would be the outer limit for a rear sprocket.

I would certainly try a racing CDI, or even a programmable unit.

I've never messed with timing. I would focus on smoothing the intake port and polishing the exhaust port first.

[Jibberwobble]

Thank you Weld.....

Just popped in and gotta rush off again so will be back later to reply properly but in answer to the gearing thing, I am running an 11" kart rear tyre instead of a big bike wheel and this will bring the gearing right down to something nearer the norm. We are pulling about 60MPH on the long straights at tracks that are about 1.2km all the way round.

It's a 200 which is the displacement limit for a 4 stroke in the regs. 85cc for a two stroke.

[katoranger]

I don't know if anything bigger than a 17t will fit. You may have to drop a tooth on the rear.

[Jibberwobble]

The trouble I'm having with gearing is that I'd like to have options to go both higher and lower than my current setup. I have a tired 24t on the back and feel that a 26 would be nearer the mark for most tracks.

Because there is not much size difference between the front and rear one or two teeth on the back makes quite a big difference. Going up on the front and back will give me ratios that lay in between just going up in 2t increments on the back alone.

In addition the 24 I have on the back seems to be very rare and all I can find to fit a 30mm kart axle is 26/28/30 etc nothing smaller, so a bigger front would bail me out a bit.

Hopefully tomorrow or thursday I will get the chance to pull the cover off and have a closer look to see how much room there is.

So is there a common mass produced front sprocket fitment that will go on my zonger? Seen some Yam ones that look the same but havent laid my hands on dimensions yet

[Weldangrind]

I believe this is the JT sprocket that fits your countershaft: http://www.jtsprockets.com/catalogue/sprocket/JTF259 It only goes to 17.

[Jibberwobble]

Originally Posted by Weldangrind

So many questions!

This is the carb I like for 200 / 230 China motors: http://www.ebay.com/itm/Carburetor-C...4979d6&vxp=mtr I jet them with a 112 main and 27 slow at sea level for a 200, 115 / 30 for a 230.

This carb looks good, does it bolt straight to the engine or are the holes a different pitch? Just a thought because if it were sitting that close to the engine it may not get in the way too much.

Originally Posted by Weldangrind

This is the intake tube I have on my atv: http://www.ebay.com/itm/30MM-MANIFOL...fb51b8&vxp=mtr Not sure if it costs any power, but I doubt it. The air and fuel are happily sucked uphill by engine vacuum.

Funny enough I've been watching that one for a while wondering if it's the answer to some of my problems, just going off to have a look through your threads for a picture of it fitted (assuming there will be one somewhere). Shipping to uk is a bit scary though.

Originally Posted by Weldangrind

The clutch isn't normally that difficult; certainly no more than an average CG125. If you can't find a mechanical problem, perhaps this would help: http://www.ebay.ca/itm/Chrome-Hydrau...4c0632&vxp=mtr

Well when I compare my clutch lever resistance with other peoples I would say mine was around ten times heavier! I can pull most clutches in with a couple of fingers but with mine I need a good grip and most of my strength. Oddly I dont notice too much when we're out on track most likely due to Adrenalin. Havent had a chance to research how it all goes together yet but will have a look into it and go down the hydraulic route if all else fails. Thanks for the link

Originally Posted by Weldangrind

You're using a 17 tooth countershaft sprocket and a 24 tooth rear sprocket? I can't believe that little motor can use such tall gearing. I figured that 40 teeth would be the outer limit for a rear sprocket.

Indeed my tiny 11" tyre on 5" rim brings the gearing back down.

Originally Posted by Weldangrind

I would certainly try a racing CDI, or even a programmable unit.

Will have a look into this and try and find something. I'm a bit lost with the CDI's to be honest, is a 125 CDI different from a 200 and if so what does it do differently? I need a spare so will get scouting, I think it's a bit more of a struggle to find this chinese stuff in the uk and the unknown import duties bother me a bit when ordering offshore.

Originally Posted by Weldangrind

I've never messed with timing. I would focus on smoothing the intake port and polishing the exhaust port first.

Ok will have a peek into the inlet/outlet and see how they can be improved, this sort of thing is up my street. I can get 11.5hp from a 40cc w/c 2stroke with the aid of my trusty dremel and it's friends! Time consuming but satisfying.

Originally Posted by Weldangrind

I believe this is the JT sprocket that fits your countershaft: http://www.jtsprockets.com/catalogue/sprocket/JTF259 It only goes to 17.

Thanks, done a bit of looking now and have found some chinky ones (18t) very cheap that I think will fit the shaft so I will go for it and see if it fits in there, I'm sure it will be fine for experimenting.

http://www.fiddyparts.co.uk/index.ph...art&Itemid=107

http://www.ebay.co.uk/itm/PITBIKE-FR...item41732a3e3b

http://www.ebay.co.uk/itm/18-TOOTH-4...item41741f3a7e

[Jibberwobble]

Whoops been all tied up for a few days pulling my old car to bits to sell as much as pos before scrapping it, it's funding the sidecar upgrades and spares.

Also been busy finding the right parts for the outfit and trying to get em all to arrive before this weekends race meeting. I've got so much to do before it's ready I'm pullig my hair out!

I now have the 18t front sprocket and it looks like it will work with a little relief to the cover.

I'm out of T-break now but will be back later with some pictures

[Weldangrind]

Originally Posted by Jibberwobble

I now have the 18t front sprocket and it looks like it will work with a little relief to the cover.

Do you mean the sprocket cover? I'd just remove it completely; that's how we do it on dirt bikes.

[Jibberwobble]

Originally Posted by Weldangrind

Do you mean the sprocket cover? I'd just remove it completely; that's how we do it on dirt bikes.

You know what, thats a bloody good idea!

As it goes I will have to stick with it for now for safety reasons, My fully enclosing bodywork is not built yet and I have some very temporary bits of chopped up second hand fibreglass on there. Eventually the seat unit will go all the way up and over the engine enclosing the chain all the way from front to back, right now it's exposed at the front which is a bit iffy really although my legs have survived a couple of chain breaks and a derailment.

To get an idea of the riding position kneel on the floor with your knees 18inches apart and your toes pointing at the floor and your butt sat 6inches above your heels. The chain passes about 1 1/2 inches below your knackers and 3 inches inside you left thigh. In an accident it would be very easy for a flailing limb to say a little hello to the front sprocket and have a little go on the roundabout!

I've done a quick mod to get me by for now so we'll see how it goes this w/e.

Cant find a good photo of the seating position and chain run just now but you sort of get the idea from this





So with the 17t sprocket roughly placed in the cover you can see the clearance situation





And the mark on the inside of the cover, I think this happened on a joining link break. We now have a new chain and will be rivetting it. There were various other issues causing chain troubles and most of the worn out and poorly set up parts have been replaced with new now. Axle, bearings, chain, front and rear sprockets, break disc and carrier all replaced.



Chop chop!





Very thin peice of Carbon sheet is now giving me another few mm of clearance.





And with the 18t in place it all gets a bit tight but I think just about doable.

[Weldangrind]

I have a numbered drill bit set that I've used for quick jet size increases. Sometimes you're in a situation where you simply can't get the jet you need, so a drill bit is the next best option.

Please show us pics of the new exhaust.

[Jibberwobble]

I'll sort a photo today.

Yes I have a nice selection of small drills but didnt have them with me. I know jets are supposed to be more than just a roughly drilled out hole but as you say in desperate times these little tricks can get you out of the dog doo.

I'm going to head for a selection around 140 kinda size which seems rather huge to me but hey! If I can get it on a dyno with lambda sensor I'm sure it would be a quick excersize to get it right.

Also do these gearboxes play up when very hot? There's a number of other small issues with the gear change that could be messing it up but sometimes not even a running drop kick would get it into 5th.

[Weldangrind]

They certainly can. With punishment like you dish out, I'd probably try synthetic 20W40.

[Jibberwobble]

Bloody hell time flies, I need a time machine! Life got in the way again.

At the last round we settled on a 135 main jet after a 137.5 showing just a hint of over rich at the end of the straight. we are lapping a little quicker now and only half a second or so behind the quickest lap of the weekend, with a small power increase we will be right up there at the sharp end.

The bodywork is completely fubar now after a visit into the scenery and burying the front end in the tyres to the point where the bodywork was squashed flat onto the forks and breaking the front brake lever off. Going to have to blob it back together for the one remaining round this year.

The gearbox worked without fault all weekend.

The exhaust is not very pretty but hasnt snapped off yet dispite breaking an engine mount thumping the chair wheel over the curbs. If you get it right the chair wheel is up in the air before reaching the apex and completely clears the curb.





I stopped looking for a carb after a 32mm unit came my way, unfortunately when I came to start looking at dealing with the manifold I realised it wasnt a 32 at all but was a 28. I feel I need to go up to at least a 30mm so will get back on it soon. Been told that the longer u-shape manifold that I have planned will be good for bottom end torque which is a good thing as pushrod motors are never gonna be screamers.

Hoping to make some updates and repairs over the w/e to the old bucket.

[Weldangrind]

That exhaust looks pretty good from my perspective!

I've been giving some thought to a perfomance cam for the pushrod motors, and it occurred to me that reducing the base circle would have the same effect as increasing lift. Do you know any old-school machinists who could grind a cam for you?