TPR 86cc Build : Part 4 : Crankcase Port Matching & Porting 

I've done that before as well. I think scribe alone is the only way I hadn't tried it before. I have an easier time with marker alone than scribing alone. Have to move the cases around a bit to let the light catch the lines sometimes that way. Sometimes I try different stuff just because.

Interesting. That's more common with larger bikes (my TMAX is like that), but I didn't know there was a 50 doing it with a full CVT engine and chain drive.

@@49ccscoot I pretty like such design,,without a CVT box there you can lean more angle when turning.Sadly it's only for 50cc version,Derbi's other scooter with larger displacement models don't follow this design.

The trench areas increase the crankcase volume, so it lowers the primary compression. Opening up the ports does the same. Basically any material removal in there lowers primary compression. Filling, like when I'm trying to eliminate a dead spot to direct flow up instead of into a corner of the original port, will have the opposite effect and raise primary compression. There are ratios that some people look for. I never measure my primary compression. It can have a detrimental effect going too far either way, but so far this has worked for me on this type of engine.

As I've done it, it should never be effective enough to starve the bearings. Plus, if any oil or fuel/oil mixture falls out of suspension, it should make it's way to the bearings as it always did. I've seen some that shield the crankcase with a metal barrier, leaving only a slit for the rod. I'm not sure if or how they deal with oiling in those cases.

Not yet. I've only had cracking of the JB Weld used for backfilling. Still never fell out of there even. Just cracked and leaked.

No. Other people have recommended the same though.

Try it on old case or something I'm curious

I would at least go over the tune if I did this to a working setup. I have never pulled a working setup apart just to port match and cut trenches to tell you for sure that it changes the jetting requirements.

You can buy twin cylinder setups for these now. Just costs a small fortune. Check out pitobread on here. He built one.

I would at least spend the time to port match. Doesn't have to be perfect, but there can be a pretty big mismatch with some cylinders. Trenching probably isn't worth it to everyone. I can't even say for sure that it makes power. I've got a whole video about it here : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-XcgFI905UGU.html

@@49ccscoot ty for your anwser ill port match and flow my cases and let the trenching aside

I have never tried porting cases with the same setup unported and ported to tell you for sure about any exact benefits or carb changes. You may want to watch this for more detail though : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-XcgFI905UGU.html

I use a Foredom SR. You can get full kits or piece together the motor, controller and hand piece. I bought their hand control, but later discovered that a router speed controller works fine for me for way less. If you get a Foredom, pick up an extra flex shaft. It has a lot of torque compared to handheld tools like the Dremel. Takes a little getting used to, but it will pull through things that the others don't so well. Down side is that it can break the flex shaft if it catches hard enough. I use the 44T hand piece, but also have the H30. The 44T is a nice small hand piece that can be held more like a pen (it is larger than a normal pen though). It uses a wrench to tighten bits into the collet. The H30 is larger diameter, but uses a chuck like a drill so swapping bits is faster/easier. Here are a bunch of links to either a kit or pieced together setup. They are amazon affiliate links. Foredom SR kit w/H30 hand piece and foot control : amzn.to/2ZPkam4 Foredom SR motor & shaft only : amzn.to/3hNn5BZ Foredom table top speed controller : amzn.to/3ckak0v Router speed controller : amzn.to/3iOFUpA Flex shaft : amzn.to/3iOtxtQ 44T hand piece : amzn.to/2RJIMYY H30 hand piece : amzn.to/3hRXSpP

A thank you would have been nice he went through all that and u didn't even acknowledge him. What a jerk.

These are about as good as it gets for these 49cc based engines as far as I know. The Yamaha stuff has less material, or at least Zuma engines do and someone on the forum has stroked an Aprilia engine and said it's similar to the Zuma cases. You can get stuff like the Malossi C-One or RC-One cases that are redesigned and use flange mount cylinders.

@@49ccscoot if your interested in something beefier, have a look into DIY Electro Discharge Machining (EDM) the ram method seems to be a good fit for this use case.

Smc rexy lomg blocks have more material there

I don't really think it's worth doing on many setups, unless you have the engine apart for other reasons. Then, I would at least port match in most cases. I don't know that MX setups would get much or anything out of trenching. I think they are generally better designed from the start. 49cc scooters are intended to be very low output, and they have tiny transfers compared to most MX stuff so I think they can use all the help they can get. I don't even think it makes a big difference on scoots, but I've never done 2 setups exactly alike aside from trenching to know. I have a video that talks specifically about this stuff : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-XcgFI905UGU.html

@@49ccscoot It's a 1994 CR80R apart for a full rebuild, and I'm going to gasket match the transfer ports, but saw your trenching vids. Interesting work!

It was from Precision Racing, but I don't see it now.

No. This is a Minarelli clone. The Super9 is supposed to be something similar, but Minarelli cylinders don't fit.

@@49ccscoot ok. What performance part for this engine Super9 big bore stroke intake pipe transmission and other racing component for that kymco

@@jovidmenie9602 www.scootertuning.ca/en/1009-kymco-super9-50-lc-2t

Precompression is overrated. To much of it makes the powerband really narrow. A tuned exhaust is a lot more important. But this does only apply to eninges with long enough port timning. Engines for use with just a muffler are more dependent on precompression. Keep in mind, a bigger volume has a lower resonance frequency. ;-)

Pipes have come a long way and they can pull mixture in. Modern pipes do a lot of work. The big issue with welding is warping. Chinese metals aren't everyone's favorite to work with either. One good thing about JB Weld or other epoxy is that if it fails I could clean it out and have it welded. If a welder warps the cases, I'm starting over again with new cases... assuming it's known and it doesn't just cause me troubles that I can't pinpoint for a long time.

Rear facing intake is what all the cool kids do. That can make a short and straight path toward the transfers without changing direction so much. Requires a custom subframe.

I'm sure it has been dyno tested, but the results may or may not have been made public.

@@49ccscoot are u on FB? So i can sent you some videos of the bikes an the drangs?

@@guidosamson682 facebook.com/brent.blades

I've used JB Weld for years and known of some people with more experience than both of us combined that have used it. It may not be the best technically, but it has worked. Most modern 2T thinking worries more about the pipe than high primary compression and having a larger volume in the cases can be beneficial. That said, no, I haven't measured the volume or tried to calculate primary compression.

@@49ccscoot also check the squish clearance on your 2 stroke this will help proof performance bye alot alot to big and you lose alot of horse power plus more wear on the piston ring to short and you burn a hole true the piston if you looke deeper into the subject you will see that your poort timings play a big keyrole in here to when comes to squish and for the jb welt yes its insane strong and yes it will do the job is it good no its not makng the crank case bigger is always a power loss unless you add back what you remove in a smart manner maluble metal i use to add what i removed back to gain peak performance i add it mostly to the rounding of the transfer ports and that stuff is alot better then jb wel plus 0 chance for cracks to apear just a tip

my true advice would be dont chip so much on the engine its way to much all you want is to make it flow a little better not to grind true it and fill it with jb welt thats why i can see good use for jb welt but not like this if you fill the transfer poort slide with jb welt to compensate for what you removed than you gain alot more out of it with alot less risk and more performance altho i must say that wall is realy thin thats why normaly your not allowded to go deep ad all there just knock the sharp corner of and be done and for the cilinder gasket you want them from the cilinder transfer ports not to be flad the harder that angel the better it is for gaining more pressure so you can vaccum suck more fuel to the cilinder so when you mark the engine wth a gasket make sure you dont !!! make that area flat that angle can be realy tight you only gain performance then and not lose so much

and since you love insane accelerating rathen then speed good ignition will do wonders over stock thats a free 5 hp from ignition alone ^^ less top speed cause you have less mass moving around to store energie but you gain insane alot of torq and that combined with diffrent cf gears ratio you can make it faster then enything you can inmagen besides elektric bikes they are just nuts

@@djemyvandermeijden794 I have checked the squish and cut the head. Keep watching and you will see other mods.