looking for people interested in top end performance modifications

I'm looking for any one in the NY/NJ/CT area that either needs a new top end on their 167fmm or wants to push performance by decking their cylinder head.

I've done this to my top end rebuild with very good results going from the stock 9:1CR to 10:1, so I'd like to see find others who might want to try or take it even further.

I'd like for them to be in my area so I can work on the bike in person, this isn't some prepackaged upgrade I'm looking to sell...
we hang out here and talk about this stuff here sometimes:

http://www.mychinamoto.com/forums/showthread.php?t=2738
Dong Fang DF 250 RTB Bobber Information

You did just head decking, or something more (porting, removing "flange" around valve seats, etc.)?

on my rebuild I did everything I could think of
- decked head
- port matching (widening openings to match connecting parts)
- flange removal on any sharp angle (especially behind the valve seats)
- rough surface polishing
- back cut valves (taking off the sharp top ridge)
- steel rods
- cylinder cross hatch
- lapping valves

from there the jets get bumped up.

I really wish I could get my hands on one of the wiseco 67.5mm oversized pistons and add a big bore to my repertoire...

And?

Can you make comparsion between "before" and "after"?

I've now had several hundred miles and can make some specific comparisons.

one main point is on long gradual inclines I am now able to hold momentum with traffic. where before I could not and would gradually slow down to a certain point.

this made me confident to try a 13/30 sprocket combination that I am now pleased with.

right now I am unsure of the top speed as I've only recently changed the gearing and because I'm having some engine surge problems at full throttle. but in the next few weeks I should know for sure.
before on flat road I could perhaps reach about 55mph max with 13/35 sprockets, now I've already reached about 65..

unfortunately it is difficult to quantize the power increase, but it is noticeable and I feel it's significant to such a low power engine.
only a dyno would tell the exact story. that's why I want to find others who will try.

Not once I had a chance to read the experiences of people who have done, so to say, "valve job" (just playing around valve seats was sufficient) on the small displacement horizontal cylinder engines.

They say that after such intervention on the engine, the zone where the intensive vibrations are starting, shifted upward by a 1000 or 1500 rpm.

Did you feel something like that on your engine?

I'm not sure if what I did qualifies as classic valve job but often I consider that all these small things including valve lapping and back cut helped add up to the final result.

before the engine work I had the same cheap Chinese tachometer, I'm not sure if something about it changed, but now my top end reads about 500 rpm or more higher than it did before..
with filter attached I could achieve about 7k, now I can reach near 8 and as I mention I have top end surge problem so I don't push it to it's limit yet.
this is also hard to quantize because I don't trust that cheap tachometer at all. but it is reasonable to suspect all these small changes lead to the higher top engine speed.

Also I feel I need to idle at a higher rpm else it tends to stall.
as well it being a bit more difficult to stay when cold.
these I suspect possibly due to the higher engine compression, but I can't be sure.

but I do not notice any difference in engine vibration. for one thing before the engine work I removed the top end engine mount bracket. I first worried any extra vibration helped caused my valve to break which destroyed the engine. so when I rebuilt it I replaced that bracket. there's no good reason to remove it and risk added vibration.

What I mentioned earlier was a basic removal of a flange... how to say... in front of the valve seats, just around valve heads. On stock head (at least, on those horizontals), valve heads are preety "drowned" in motor head and when they start to open, in first few milimeters air flow is very reduced. Allegedly, by removing this "flange", air flow improves so engine pumps bit more power (this I understand), and, as I mentioned - vibrations are starting on higher revs (???).

BTW, did you do something with valve springs, try stiffer ones or something else?




Damn, my English is killing me!

I understand your what you want to say.
I tried to remove any ridge (flange) that I found. when the valve seats are inserted in the head they don't perfectly match the contour of the port, therefore a ridge is made. I did my best to remove those.

but remember here we are talking about a very low power engine so the theoretical gain is not that much anyway .

I did not try any special valve springs. I used the new valve springs that came with the new head.
actually I was very disappointed with the new springs as they arrived rusted, they did not seem to me quality material.
but they were stiffer than the old ones and as far as I know, my valve failure could have been caused by the old valve springs so I used the new springs.
so far so good.

Quote:

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Originally Posted by axa

but remember here we are talking about a very small power engine so the theoretical gain is not so much anyway

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O, I stop believing in Santa Claus long time ago. :icon10:

Say, what you use for smoothing rough surfaces inside ports? I saw guy who, after cutter job, used piece of "Mirka's" abrasive mesh, cutted to form some kind of flaps, fixed on a splitted stud on a common drill or dremel. I was surprised when i saw results. Plus, IMO at least, this way is practically "idiot-proof" and the chances for something to go wrong are significantly reduced, which is great for us, weekend mechanics.

http://www.harborfreight.com/media/c...mage_13065.jpg

"Old school". :thumbsup:

Here's abrasive mesh I mentioned in action - https://www.youtube.com/watch?v=r8MZbYQHtz4. Maybe it'll come handy on some of your next projects.

I might say that in the video is old school using home made tools, and my way is new school as the cartridge rolls surely came more recently

for sure if doing work like in this video, you must be prepared to do more work.
as you can see he makes many contacts with the valve seats and valve stems are already removed.
for sure he need to take head to pro machine shop, or at least use pro tools to cut new cable seats and insert new stems.

by the way you might be interested in this article about intense modification of 167fmm:

https://rideapart.com/articles/how-t...200-motorcycle

In my part of the world, "old school" would be stones of different hardness, conical, cylindric, spherical - you name it. An I hate them all - blue, red, and f.... white ones. :icon10:

I like this trick with abrasive mesh because it seems to me you can not screw things in a second, as you can with other abrasives, plus you don't have to have a steady and "artistic" hand in order to get decent looking port. It is certain that I'll try something like this when I get a chance. Finally I have some use for the old "Peugeot" motor head.

You mentioned valve seats cutting. Do you have experience with a hand cutters? With which is easier to do the job - carbide tipped or those classical, made of tool steel?

A propos "Ride Apart's" article: I'm interested to see that camshaft with a new lobe, more than anything else they did. I think (but do not rule out the possibility that I'm wrong) that no one in China has offered to the market modified camshaft for CG clones. Looking for one?

never seen any custom cam for sale on cg engine. I never cut valve seats. iy require more tooling than I have, must be very precise.

OK so when u use this kind of flap abrasive let us know how it goes.

so through a series of mistakes I ended up blowing my head gasket. a combination of under torqued head bolts, low octane gas, sharp edge left from head deck caused hotspot detonation.

I didn't oil the head bolts when assembling, I didn't re-torque after first use, after disassembly i found them very loose.

I was using 87 octane with the 10:1 compression, this caused a distinct high frequency ping I could hear but not recognize as detonation...

and disassembly i was very suprised to find i left newly created sharp edges created when the shaved head brought the edge of the larger intake valve closer to the surface.

also excessive after fire should have been looked into.

needless to say I fixed these issues as well as resurfaced the head removing .007" more for a total of .042 or approximately 1mm total head reduction.
I have not calculated final compression ratio yet so I won't speculate now. so far so good

With so much "shaving" of a head, maybe you should fit injector pump and convert it to diesel. :poke

that's crazy talk :p:eek:

Spare parts available for order.

http://www.rotoscopers.com/wp-conten.../acme-wile.jpg


:riding:

"About carbie: I think that some CV carbie would do better job (for everyday riding) than plans slider type with acceleration pump.

But, IMO, there is one big thing that limits you significantly - this pushrod design with only one lobe and, as you realized earlier, non existing tuning cams.

Everything else you've already done....

BTW, did you tried to measure compression (not compression ratio, which is anyway just arithmetic mean)? You know... gauge, hose, spark plug hole, cranking... and result in... what you use in your part of the world - PSIs? On dry and with few cc of oil inside cylinder?

As you can see, my English limits me a lot, so I would mention few things for you "to think about". I'm not regular in this thread, so I'm sorry if I missed some mods on your bike.

If you already experiment with low octane gasoline and increased compression, you could think about buying adjustable or programmable CDI unit. Those adjustable are available at "Aliexpress". It could be handy to have possibility to adjust ignition angle and smooth engine's running.

Another thing is oil cooler. There are some kits with engine head cover with oil inlet and outlet, set of hoses and radiator, and what is important, it is "bolt-on" solution.

I believe that adjustable ignition and oil cooler could, if not prevent, than at least reduce, engine surges you mentioned half a year ago."


I did measure cr sometime ago, but didnt take note becuase it was on a freshly honed cross hatched cylinder, so it couldnt get any better...

Can you point me to a programmable (variable) CDI, preferably one i can get easy in US like on ebay.
When i looked into it there i couldn't find enough information to know which will legitimately adjust the timing and will work with the 167fmm.

Yes i still have the strange surging mainly when loading the engine, but also generally when approaching opening throttle.
To figure out if it is the air fuel mix, Ive started to ride with small main jet and replace filter with velocity stack, and i will work my way to larger jet and closed filter."

But something tells me this surging is not mix problem because ive had mix issues before that did not result in strange engine surges.

Also an oil cooler might also be a useful item, but its hard to know if i have a heat problem and if the unit for cg engine is effective. I have my doubts to its design
Do you notice there is no pump and this engine has lower oil pressure, so im skeptical if the oil flows well through.

PS. your english is fine. no need to conciser it

Heh, for those programmable I've heard right here, on this forum. Our "insider", guy we know as "humanbeing", few years ago left few "Taobao" links to those CDIs. Where are those links, I really don't know.

Basically, you get CDI box with USB interface and some software to do the job (it seem to me like something I could manage myself). There are three different preloaded ignition patterns (kinda, first has constant angle for triggering spark, second varies angle depending on revs in that manner, third has some other twist, and the last is left for user to custom fit it. As I said, this procedure, creating custom made ingition curve, didn't look to me like "mission impossible" even for noobs. Price? Um... it was long time ago, but i think it was low three figure.

And there are those adjustable CDIs. As I understand, they have variable angle and some more or less generic ignition timing curve, but you can move this curve in amplitude of 4 or 5 degrees with a plaing tiny screwdriver. It is not much, but IMO, it will do the magic. They look like this - http://www.aliexpress.com/item/Gy6-r...74_75,201409_1 .

About surging. Here, in my neighborhood, this happens after too tight boring of a cylinder, when someone rebuild engine, especially when it is two-stroker. Simply, piston doesn't have enough space to expand. Plus, most of our C-motos are air cooled so thermal strains are different comparing to liquid cooled engines. Do you know, how much differs diameter of your piston and cylinder? And than, there is this urban legend about strange thermal properties of a alloy in Chinese pistons (if you so far didn't fit this "Wiseco" you mentioned), and when you add increased compression... Sh...Surge happens. Bottom line: I think that problem is in those two.

I fit some bolt-on oil cooler (take-off plate on a head, pair of hoses and a radiator) on my lil' 50 cc horizontal engine. And you know - thing works! It really takes out the heat and dissipates through radiator. I couldn't quantify how much this thing decrease oil temperature, but I know that oil hose fittings and radiator can be pretty hot. At the end, you can monitor oil temperature before and after fitting oil cooler with those handy dipstick thermometers.

About "no pump": I thought the same thing about my horizontal, that this is engine with a bath splash lubrication, but there is a small trochoidal pump that pumps oil into two lines toward head and crankshaft. Yes, it is low pressure pump (my engine pumps app. up to 2,5 Bar when the oil is cold, and about 1 Bar on working temp, but still, pumps oil nicely. Plus, internal volume of a oil cooler "appendix" (radiator and hoses), on my engine is relatively small - just around 100 cc, so this is not so big "detour" for the oil flow. IMO, if are the is no "bottle necks" (narrower passages that is) inside inlets and oultlets, radiator and hoses, this contraption should work nice even on a low oil pressure engine.

Here's one of oil cooler sets for OHV "Honda" based clones: http://www.aliexpress.com/item/Mediu...74_75,201409_1 .

One more thing. We talked about valve seat cutters in their hand tool version. One word - "Neway". Oh, they are sweet, great for DIY, but their pricing knock me down.

Quote:

---

Originally Posted by Zorge

Heh, for those programmable I've heard right here, on this forum. Our "insider", guy we know as "humanbeing", few years ago left few "Taobao" links to those CDIs. Where are those links, I really don't know.

Basically, you get CDI box with USB interface and some software to do the job (it seem to me like something I could manage myself). There are three different preloaded ignition patterns (kinda, first has constant angle for triggering spark, second varies angle depending on revs in that manner, third has some other twist, and the last is left for user to custom fit it. As I said, this procedure, creating custom made ingition curve, didn't look to me like "mission impossible" even for noobs. Price? Um... it was long time ago, but i think it was low three figure.

And there are those adjustable CDIs. As I understand, they have variable angle and some more or less generic ignition timing curve, but you can move this curve in amplitude of 4 or 5 degrees with a plaing tiny screwdriver. It is not much, but IMO, it will do the magic. They look like this - http://www.aliexpress.com/item/Gy6-r...74_75,201409_1 .

About surging. Here, in my neighborhood, this happens after too tight boring of a cylinder, when someone rebuild engine, especially when it is two-stroker. Simply, piston doesn't have enough space to expand. Plus, most of our C-motos are air cooled so thermal strains are different comparing to liquid cooled engines. Do you know, how much differs diameter of your piston and cylinder? And than, there is this urban legend about strange thermal properties of a alloy in Chinese pistons (if you so far didn't fit this "Wiseco" you mentioned), and when you add increased compression... Sh...Surge happens. Bottom line: I think that problem is in those two.

I fit some bolt-on oil cooler (take-off plate on a head, pair of hoses and a radiator) on my lil' 50 cc horizontal engine. And you know - thing works! It really takes out the heat and dissipates through radiator. I couldn't quantify how much this thing decrease oil temperature, but I know that oil hose fittings and radiator can be pretty hot. At the end, you can monitor oil temperature before and after fitting oil cooler with those handy dipstick thermometers.

About "no pump": I thought the same thing about my horizontal, that this is engine with a bath splash lubrication, but there is a small trochoidal pump that pumps oil into two lines toward head and crankshaft. Yes, it is low pressure pump (my engine pumps app. up to 2,5 Bar when the oil is cold, and about 1 Bar on working temp, but still, pumps oil nicely. Plus, internal volume of a oil cooler "appendix" (radiator and hoses), on my engine is relatively small - just around 100 cc, so this is not so big "detour" for the oil flow. IMO, if are the is no "bottle necks" (narrower passages that is) inside inlets and oultlets, radiator and hoses, this contraption should work nice even on a low oil pressure engine.

Here's one of oil cooler sets for OHV "Honda" based clones: http://www.aliexpress.com/item/Mediu...74_75,201409_1 .

One more thing. We talked about valve seat cutters in their hand tool version. One word - "Neway". Oh, they are sweet, great for DIY, but their pricing knock me down.

---

Zorge I finally figured out what the cause of the engine surges were.... as i reported it happened during stress, on climbing , but also quick roll of throttle. it was simply because my clutch was slipping.

immediately recognized it when I mistakenly dragged my hand on the lever during acceleration, I then loosened the cable and no more surges.
now I can roll WOT while on incline and hold a good speed.


I'm quite relieved as the surges started soon after all my engine mods, i want sure if i over did things... I'd like to think I gave it more power but probably i just misadjusted the tension and forgot about it.

I might need to find stiffer clutch springs though. I hadn't looked into it yet, are these available?

Oh, that kind of surge! I thought that you experienced surge with full stop of a engine.

About clutch: you know, if those stock springs are bit tired, maybe "Honda's" (note this - "Honda's" (or gooooood substitute, from reputable manufacturer)) genuine CG springs will do the job.

Or, you could, for the sake of the experiment, play with washers to get bit stronger preload of those springs, or to add some extra ring in a "sandwich" made of metallic discs and friction plates.

Unfortunately, I do not have in front of me this clutch assembly, and I can not weigh - to do by the book, or to try"something completely different".

Quote:

---

Originally Posted by Zorge

Oh, that kind of surge! I thought that you experienced surge with full stop of a engine.

About clutch: you know, if those stock springs are bit tired, maybe "Honda's" (note this - "Honda's" (or gooooood substitute, from reputable manufacturer)) genuine CG springs will do the job.

Or, you could, for the sake of the experiment, play with washers to get bit stronger preload of those springs, or to add some extra ring in a "sandwich" made of metallic discs and friction plates.

Unfortunately, I do not have in front of me this clutch assembly, and I can not weigh - to do by the book, or to try"something completely different".

---

genuine springs seem like a reasonable solution. With each new set of valves I noticed springs of different strengths, seems to me clutch consistency wouldn't be any different.

I've heard of adding plates before but that seemed a solution for too much power... surely don't have that problem here

Adding extra plates (or some other way to keep them tighter), in case with C-motos, is also to compensate worn friction plates or new plates thinner than stock (it seems that it is not so rare occurrence).