yup, My team driver has a new Losi and it's equiped with a Pro Twister .21R. I'm running gas truck with a Pro Twister .12R. Stop buy and say hi, i would like to meet ya.

Ive done quite a few engines. Mainly flowing the sleeve. The cranks were quite good so never touched the crank.
The only timing changes Ive done was raising the exhaust port by.5 or 1 mm. This took away some bottom end and better top end.

On My SH28 6P I raised the exhaust port and flowed the engine. This beast was just way too powerfull. It revved better but snapped the rod. This mill cannot take repeated high rpm, top heavy.

Ahhh all the timing and porting advice ive gave to my good buddy supertib and he doesnt even mention me[] LOL. Its ok buddy i forgive ya. But i may have to charge u now to use my X-Dyno!! J/J

This engine moding thing is a huge learning experience! Ive been doin it for years and i still learn more and improve my engines all the time. And theres nothing more satisfying then watching an engine u modified improve before your eyes. It still to this day gives me that rush So for u guys that are wanting to learn how to port your own engines with great results dont give up. It takes a long time to really get to know these engines, but in the end it is VERY rewarding!

So after you cut the ports up, what were the final timing profiles of these engines you modded?
Crank induction duration?
Lateral intake port durations?
Boost port duration?
Exhuast port duration?
How many degrees after TDC does the induction port open after TDC?

I too am still learning about engine modding and am trying to learn as many timing profiles as possible to determine what each profile does as far as low RPM performance, mid-RPM performance, and high RPM performance.

Up until this point I have not radically changed the timing of an engine. I mostly flow the sleeve and wont change the timing profile as that is the characteristics of the engine. I do not want to change that. By lifting the exhaust port I am only moving the power band ex let say the power band was 7000rpm to 34000rpm, it will be 9000rpm to 36000 rpm.
I recently changed the this on my P5X.
The engine had just rediculopusly too much bottom end. Now I find good bottom with a phenomenal midrange and very good top end.

Everyone modifies in their own way. I only mod for more overall power and economy, maybe if it needs better top end.

On the past few engines I modded, most recently, 2 Axial .28 Spec1 RRs, I did not alter the timing profiles. I did entirely sleeve work and did flow mods and touch-up work on my RR sleeves. In particular, I matched the exhaust port of the sleeve to the exhaust port of the block. From looking through the back nozzle, an unaltered sleeve is poorly matched to the block port; you can literally see a whole ot of brass sticking out where it should not be at all.

Interesting subject,I'm new to this forum, but may open a new can of worms,I build motorcycle dragrace engines, from complete cylinder heads ,extensive porting,flow testing, seat and guide installation serdi valve jobs etc.4- cycle but anyway ,Knowing what I know about piston port 2-cycle engines ,I have a question? When you mill a cylinder head to make the combustion chamber smaller you raise C.R (compression ratio),correct? when you remove material from a cylinderhead chamber it increases c.c's lowering C.R correct? Then what happens when you remove a moderate amount of material from the lower end,Crankshaft, cylinder sleeve, cases piston skirt,etc. ? My point being, My take on piston port 2-cycle engines whether it's nitro or gas, Their are primary and secondary compressions going on ,again I am just asking a question , and not trying to stir the pot, actually it's a three stroke, think about it,When the piston travel's upward and the crank window opens and its drawing in fresh fuel charge on the compression stroke , when the fuel ignites driving the piston down on the power stroke it also exausts and uncovers the transfers to allow the fresh charge into the c.c (Combustion chamber) from the crank case performing three actions in one revolution , so my question being ,By removing material from the lower end any at all seems to me it would make the secondary compression lazier on discharge through the transfers, in other words would compromise velocity, and make charge motion slooooower, and yes I know there are many variables, maybe these engines are allready to small in the lower half , where is the ellusive balance,Just My 2 cents. Thank's Mike R.

Mike...that's exactly right...removing material anywhere inside the case will effectively lower base compression, so you have to tread lightly.

When I mod a sleeve for example, I basically just radius the sharp edges in the fuel/air mixture's flow path. When I do a crank, I'll bell mouth the opening of the induction passage where it opens into the case, and polish the passageway if necessary...and sometimes add silicone in the area immediately under the carb. I will add here though that I don't race, and just do my own mods for bashing, so I'm not looking to get the max out of any one particular engine, but basically to improve efficiency somewhat.

If you go and remove a lot of material from the crank, sleeve, case, etc. and increase the internal volume by a substantial percentage, that will lower the flow velocity, soften the bottom end torque, and you'll need to work the ports and timing for top end power to get something back, or you'll end up with a doggy, less powerful engine than you started with.

here is a modded Jammin JPX .21 that I just completed..... this work is done 100% by hand using the files in the pictures.the rough surface is deliberate, I usually will polish up a sleeve for taking pictures, but I am lazy today..... so this is how i would run the sleeve in my motor......this is a fully altered motor with pretty extensive port modifications.... Notice how the exhaust port lining is brass not chrome ?

nice job supertib.

did you change the intake timing? because it dosen't look like it.

can you give me a link to where you got those files? I found some but there not that small, and there not diamond files.

the intake timing is altered slightly ( I still have a little more work to do yet FYI) ...notice the front corners of the transfer ports ?

unfortunately you will likely never find these exact files, as they are only available locally to me in a very limited supply.. I would very much love to find a more available source of these fantastic little files ........ Be warned using these files to alter ports takes an extremely long time and also it can be extremely difficult to cut cleanly... The chrome is very tough and very difficult to remove nicely., you will likely mess up several sleeves before you get the feel of the metals......

I did see the corners, but I didn't think that was veary much. my files are normal and there about 8" long, I think they will work but the chrome is harder than the brass. I got a old sleeve to work on then the hyper 21 8-port before I start on any good engines.


how about these http://item.express.ebay.com/5-Mini-...mdZExpressItem

those will work......... regular files will never cut the chrome...they need to be diamond files.

I'll try to talk my Mom into ordering those for me

I want to start, but I need to finish my other project first. oh, you should have got an e-mail with pictures.

Your Mom!?

Yup, since I'm home schooled, I'll if she'll count it has school stuff I am only 14

supertib I sent you a few emails, are you getting them?

jb, I would not have expected you to be 14. Most 14 year olds don't have the patients to research somthing like this. But anyways. I have read through a few threads. One being about 14 pages long and then also through this and a few otheres. Are there any ways to change the timing profiles without getting into the chrome on the sleave? I dont have access to diamond files at the moment. I am working on modding a boat engine, if anyone has ever done any of this. It is an aquacraft .15, from a nitro hammer.

my normal files I have will cut the chrome, but it takes a long time. you can get a set of diamon files on ebay for $10


you are not the frist person to say "I wouldn't have tought you where 14" or somthing along those lines

Good selection of files here...
http://www.arceurotrade.co.uk/

They on the LH side under diamond tools.

.

your dreaming if you think normal files will cut the chrome......as well it also takes quite some time to cut even with diamond files...... This is not something to be taken lightly..

I should of known you where going to say that, you're almost so predictable about modding engines and piccos its almost funny. (I mean that in a good way) my files are dual cutting files and they did cut the chrome (not the timing) I was messing around cutting the the bottom of the sleeve below the boost port, and they did cut the chrome, I'll try to get a picture and post.

know they would work for timing since it takes a lot to cut the chrome with these, and they are too big to do timing. basicly they are for outside the sleeve modding only.

I beleive that they will cut on the bottom of the sleeve, as I use regular files for that too ....LOL but cutting upwards into the chrome lining of the port is a much different animal. Please go try a old sleeve and let me know how they do !!!! . I honestly cannot see a non diamond file being able to cut the timing........

I can't beleave I'm saying this to you, but did you read my post? I said that they will NOT work on the timing but they did for cutting the bottom of the sleeve like this picture (this not my sleeve but what I did is the same thing.

LOL I was posting when you posted, and I didnt read your thread till I had already posted !!!!!

you asked me about cutting timing..I told you what you needed, then you commented your regular files can cut chrome anyways...So I told you that you were wrong, you need diamond files to alter timing........... dude the whole thing your asking here is altering timing...using a big rasp file to cut the bottom of the sleeve has no bearing on cutting port timing...so why bother mentioning your current files will cut chrome ????? to me it seems rather pointless

well, theres two things about what I said. one was that my files (normaly harden steel dual cutting files) can cut chrome but they can not cut timing because of their size, if the ports where about 2-3 times bigger then what they are then they would work, but diamond files are best/easiest way for modding timing.