A35 Porting

Well, after looking through old threads, there isn't too much on porting an A35, so I thought I would start one. Doing this more or less to show what Ive done to mine, and am continuing to do, as well as give a place for posting your A35 port work. Enjoy!

This is the port job I ran on my first race recently. Other than the bike not being geared right at all, it ran VERY consistent. Paired with my other mods the bike had a great midrange and decent top end (which would have been GREAT had I had it geared correctly):

Just got finished with some more work... this is where I am at now, but Im not finished. Im waiting on a rt. angle pencil grinder to come in the mail so I can work on the transfers and get my blowdown timing where I want it. Also, my port mapping skills suck... the map makes the ports look all funky, but they are actually nice and straight/etc. Sorry, no measurements, I havent even run this job yet:

This port job will be matched with the work I did to the piston. Here's to hoping it doesn't destroy itself :(

Feel free to add what you want... or complain... whatever.

Re: A35 Porting

Did you have to run a spacer on the base to get the ports to open fully at BDC? The main difference from the one I'm working on is that I'm keeping the intake bridge. I'll be running a single ring piston with the locating pin on the intake side. That should allow me to widen the exhaust a bit, which you can't do much of with the stock piston due to the close proximity of the ring ends to the exhaust port.

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Im thinking about a spacer, the fact that the transfers dont open all the way bugs the crap out of me, especially since I only need to raise them like a mm to get my blowdown right (and even then I still wont be getting all the flow that my intake/carb is capable of). And Ive contemplated finding a puch piston or something that has the ring ends away from the exhaust, I really want to widen it, but can't anymore. I hear you can move the locator pins, so if I figure that out I may go that route. I'll post stuff back here too. I'm not the type to horde any possible advances I might make lol (edited)

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Also, I feel I could MAYBE squeeze the ring ends into the gap between the intake and transfers so I can open the transfers toward the exhaust and make the exhaust sort of a T shape (if that makes sense).

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Well, decided not to go with a spacer because I didnt want to play with my exhaust timing anymore for now. Decided to do some work to the piston instead. The pics are from my phone and do no justice to it. It actually looks pretty sweet. I went along the lines of what some people have done to the exhaust side of their piston to increase duration, but I spent like an hour just getting the shape right on this. I tried to make it swept so that the carter flow isnt really affected (this was one of those times where the fact that I have OCD really helped...):

Re: A35 Porting

locator pin removal post #5

http://www.advrider.com/forums/showthread.php?t=597075 (edited)

Re: A35 Porting

Ok, ran that port job from the second picture tonight, along with the piston chamfering. Also, note this is with many other mods. Setup is as follows:

1992 A35

Stock cylinder, ported to pic above (with piston mods also)

Custom intake

Malossi 4-Petal Reeds

HPI CDI ignition (just put it on today, started first kick)

Mikuni VM18 carb (Jetting: 70 main, 15 idle, 4F18 needle at leanest setting)

UniPod air filter

Case matched

Techno Circuit Exhaust, Baffle removed

Tried out 26:28 gearing tonight (this is setup for racing in the Cherry Valley Cup)

Holy crap, runs like a whole different bike. The porting changes mixed with the gearing... jesus. Wants to wheelie off the line and into second, just a little into second gear it hits the pipe and rockets up. Still haven't hit top speed, didnt have enough room and I was on gravel (aka scary shit).

Also, this is in the works:

And before you ask, no, its not gonna fly apart. I welded the outer rim of the two hubs together where they meet, can't see it in that pic. Just did this on a spare bell, Im gonna throw it in and see what happens (if it explodes, it explodes). (edited)

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porting does what it suppeose to:)

quote "Wants to wheelie off the line and into second"

i see no pic but i see pics on other treads

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Going from a 22 rear to a 28 also has a lot to do with the wheelie off the line. I'll bet it turns some insane rpm's at wot.

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Yeah, I geared it that way on purpose. Im racing my bike at the Cherry Valley cup in Lafayette, NY (theres a thread in Gen Forum about it) and at the last race, everybody was geared way low, turning way high rpm. I was just cruising basically, got my ass burned out of every corner (I could sorta hold with everyone on the straights, but I could never get my RPMs up high enough to hit the pipe). That was with stock 26:22 gearing, I didnt own any other sprockets at the time. Im taking the sprockets I bought with me to the next race and Im gonna see how it reacts, if it doesnt get out of the corners like I want during practice, Im gonna go 24:28. I have a 31 rear from a streetmate wheel, but I think thats just overkill.

All in all, Im building the bike to be a screamer, and so far, it does scream. If I go 24:28 and it runs well, I may still play with my exhaust (my timing right now is about 170*).

Oh, and for OG vandal, here is a pic of said bike:

I have a shitty ass phone video of it running, so I won't post that. Ill take my good camera to work if I can find my tripod and Ill do a run vid. Still wont be able to really get to top speed since I dont have any asphalt to ride on :/

Re: A35 Porting

NEMA Victor (3 Knees Down) /

The major downfall to the tomos racing on that track is getting it to shift down. Having short gearing will cause you to shift faster with the stock gears (in my experience). The straight will be your best and worst part because you'll be in second gear going into the turn, but you will catch up quickly with proper gearing.

Re: A35 Porting

@Victor, yeah, that's what killed me last time. Turn two was a bitch and I was just barely getting out of there. But now this thing goes faster than it did before and it gets there a whole lot faster. I really don't know what it will do until I get it to the track though, so we'll see what happens. More or less I want to at least be able to keep up this time.

Re: A35 Porting

what frame is that?

Re: A35 Porting

tomos colibri

Re: A35 Porting

that intake and carb position is sick!

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i like how this one is too, and timing on that cdi looks easier.

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Yep, tomos colibri with crossbar added. I couldnt get gas to the carb with the tank in the stock position so I had to do it (didnt really want to). Intake was made by myself. I would put the carb at an angle but Im always weary of doing that... just me I guess. I need to make a better intake with a radius to it rather than that angle, but I dont have a mandrel bender and I havent had time to do the sand/squash pipe method.

And boy, timing the HPI is cake compared to the stock points system. I hated having to put the flywheel on and take it off, put it on, take it off, etc. And you dont have to worry about the points gap either.

Re: A35 Porting

So, this has turned into more of an A35 Tuning thread, but it's all good. Thought I would add a bit from my testing the other day.

Went down to a 65 jet because the 70 was still reading slightly rich on the plug. I dont have a temp gauge so I don't actually know how hot it's getting in there, but it doesnt 4 stroke as bad in the mid range as it did with the 70 main (and opens up a little better on top). Also switched out to a 4F15 needle, slightly richer needle but in combo with the 65 main jet, works great (at middle position right now). Also found out that the 15 idle jet was too small, went to a 17.5, still too small (would only idle with the choke on). It ran fine the other day with the 15, but maybe it was something about the weather, don't really know. May go back to the 30 as I don't really have any other idle jets and although the 30 is rich, it idled pretty well.

Still wishing I had some asphalt to ride on to really get some testing in, can't ride this thing on the street (Id get pulled over in a millisecond).

Re: A35 Porting

Ok, thought I would resurrect this thread. That second port job I posted way back when is a beast when coupled with the right pipe. I ran it at the last NEMA race this season with a new custom pipe I designed, along with down gearing some more to 24/28. Absolutely friggin rocked. My top speed was most definitely higher than it had been with the techno circuit (even with the lower gearing) and mid range acceleration drastically increased (to the point where it wants to throw you off the bike when the pipe hits... anyone is welcome to ride the bike if they don't believe me haha). Also note that I changed out the clutch springs to 30lb on BOTH clutches, much much better. I just got finished this evening raising the exhaust duration some more... Ill post a new port map when I get it done. I'm hoping to get my RPMs up to at least 13K+ by the time I'm done (Probably will end up gearing at 24/31 when I'm done too, top speed will be similar but I'm more looking for the get-up-and-go).

Also, don't use this gearing or porting for everyday use, this is race only stuff. Although the acceleration is pretty fucking sweet...

Re: A35 Porting

It looks like you made the exhaust to high, you are going to lose some compresion from that, I focused more on widening it and straightening the tunnle from the port to the exhaust allong with polishing it to help the air move.

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You do realize that I have run the cylinder as it was and it ripped right (and I was only at 172* exhaust duration which is kinda conservative)? Ive widened the exhaust port as far as I can without hitting the ring ends, I havent relocated them yet. And I milled the stock head to compensate for any compression loss, plus I have a high comp head to throw on since I did the most recent work to compensate even more. Also, the port itself is very straight from what work I did to it, and it is polished to mirror smooth. I can't do much more or I will cut through the casting (I'll have a hole pretty much).

Not trying to be a dick, but do you actually know anything about porting? What are your port durations from what you did? What pipe are you running? If you just hap-hazardly port and don't match different variables, your bike will run shitty. I planned out what I did and I was very happy with what I did. You wouldnt want to port your bike like mine unless you planned on racing it, for general use my setup sucks.

Re: A35 Porting

- Summerai - Drew /

Put a puch piston up in that bitch. hey I'm exited to see your revised port job.

Re: A35 Porting

I had thought about using a puch piston, but I would have to cut in the windows and all that jazz again. I sometimes sort of regret cutting out the bridge in the intake because I could have gotten a single ring piston with the ring end 180* from the exhaust, meaning no need to relocate the ring end guides. But, with how light the piston is now, I think I'm fine with two rings... It's done well so far.

Oh, and I have the cylinder with me now, I just havent had time to sit down and do the map. I'll get that up ASAP.

Re: A35 Porting

- Summerai - Drew /

Stock transfers?

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As of right now, yes. But, I raised the intake port almost 2mm and the piston chamfering I did fixed the problem of the transfers not fully opening. I don't own a right angle pencil grinder to work on them unfortunately, If I did I would raise them a bit to get my blowdown where I want it, as well as widen slightly for more port flow area. Although, they are enlarged where they meet the case (I case-matched to the enlargement as well).

Re: A35 Porting

Well I'd say the job I did on mine worked fairly well for my purposes. I had assumed since you had made a reference to racing that you were already running a hi compression head on it, thus heightening the exhaust port would cause the piston to seal the cylinder latter causing a loss in your compression ratio. Right now mine is a daily driver and resembles your first map quite closely, I didn't want to do a lot of other adjustments so I bought this piston ( https://www.treatland.tv/tomos-stock-meteor-piston-p/tomos-stock-piston-12pin.htm ) and place the ring ends upward so they would be just outside the intake then cut my own opening in it to match the intake port, thus allowing me to widen the exhaust without having to heighten it more than 2mm and still getting the desired results, and at the same time losing minimum compression. along with this I also welded up my own 20mm intake manifold to run an sha carb. sadly I cant afford a great pipe right now so im stuck with the jamarcol fuego thats on it, but i was able to get a puch hi compression head. so all in all id say im doing fairly well for a daily driver.

Re: A35 Porting

what exhaust would you suggest I get for it when I have the cash.

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Yeah, good choice on that piston/cutting the window(s). The reason I had to go that high on exhaust is to get the RPMs up where I want them, again, purely for racing. I dont really think you would want a bike that does 11K+ for daily riding.

Btw, you dont need to be able to afford an expensive pipe. Build one... that's what I did:

Re: A35 Porting

Well, it depends on what you want to get out of the bike. I dont really have any experience with pipes because the only one Ive ever bought was the techno circuit. It was ok, but not the best for what I wanted. It has a good mid-range though, and is relatively inexpensive. I have built my performance pipes though (designed for the cylinder).

Re: A35 Porting

well that's the problem I'm having now the rev limiter on the CDI is preventing me from going any higher, and I have to run a lower gear ratio because the whole ride out of my neighborhood is up hill, that pipe looks bad, how far down the header does the chamber start, I don't want want to build one and find out it sucks more than the fuego.

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