Maico 326 revisited

[JC]

Gents,

Just revisiting this topic after catching up on back-reading on page 5.

Have any of you followed thro on building one? Mention was made of using a 400 sleeve/barrell, but the 400 engine had 13mm longer stroke. (83 vs 70mm) I would have tho't that would cause major problems in using a 400 barrell or sleeve on a 250 bottom end.

I would have tho't it better to make a new liner to suit the 400 piston (77mm) & 250 stroke. I recently measured a 250's cases & it seems the cutout in the cases for the cylinder spigot is sufficient to take a 400-size sleeve, but not sufficent to take a sleeve made for an 80mm Yam 360  piston w'out machining (which would give 351cc).

Another possibility is to adapt a Yam top-end, something I wanted to do back in the day (as mentioned in another post), but never had the resources.

Mention was made of the Maico at CD2 featured in VMX. I talked to him/them at CD5 & by then he/they had 2 modified 250s. He was a little guarded w his info, but it seemed both had specially made sleeves, one to take a 77mm 400 Maico piston, & the other to take an 80mm Yam 360 piston.

Does anybody on the forum know more about those bikes?

PS. Mark, I think the SA racer who built/raced a 326 was Geoff Flink wasn't it?

[firko]

That's him, Geoff Flink from Port Pirie. My 350 squarie is actually a factory 326cc. I rode the bike Geoff Flink did for another bloke (can't recall his name atm) and it was a sweetie. It transforms the ordinary 250 into a rocket.

[Maicojames]

Kawboy, with the booming US economy, I have been very busy just keeping the elecrticlty and water on . I do have a 250 AW engine and a std 440 piston, though I planed to locate a 400 piston. As far as the sleeve in the 250 barrel, check out the post I started about the 75 326 that Big K sold-I think womabt bought it. It has a sleeve in the 250 barrel. I thouhght about using the 400 cylinder and machining down to use on the 250 lower-as the porting changes when you take a 250 cylinder out.
 Sure you can tune the intake and exhaust length, but the transfer area is reduced. That said Big K's old 326 reputablty runs like a rocket-so it may not be a problem .
My thought was jsut to optimze the combo as much as possible, and from everything I have learned-transfer area is the most signifigant part of power production-all other factors tuned optimally , of course.

I love this discussion, would love to get the $ to pursue it-I am not sure when I can ever rake up the $ to try to buy my old 77 440 back, so I really want to build a 76 chassis with a 326 engine. How did you measure the 250 lower opening? I suppose a digital caliper would suffice? I will go measure mine and reporrt back.
Thanks,
 MJ

[JC]

MJ,

Yes I did read KigK's posts. As I recall he only mentions using a 400 piston (not sleeve). Others seeemd to have jumped to the conclusion he used 400 sleeve as well.

Unless we're talking about a blank 400 sleeve, I'd have reservations about it working w a cut down 400 barrell/sleeve w'out a lot of juggling around, grinding & machining to get the porting/timing & barrell height right. A 400 sleeve w the ports cut in for a 400 engine still has an 83mm stroke. A 13mm diff in stroke is a big diff to get ports & timing right. (Seems to me there was a bit of misleading info on the previous 326 Maico posting, curently on pg 5 of the Maico Marque Remarks, but I could be wrong)

I don't have the specs for a radialfin 400 engine, but I do have the squarebarrel 400 specs. If the radial is similar in port heights (& I suspect they are - they seem to be typical of Maico engines of the day) you'd have to take about 10mm off the top of the sleeve to get the ex & transfers anywhere near the ballpark & lining up in the 250 barrell, & you'd have probably cut off the flange on the top of the sleeve by then, which would brings other (fairly major) complications. And you'd still have to adjust the bottom of the barrell to get the piston in the right spot (which I think would still cover about 3mm of the ex & trans ports at BDC). Not insurmountable, but not straightforward/easy either.

The bottom of the inlet in the sleeve will be a fair bit lower than the port in the 250 cyl, but thats not a bad thing if the port in the barrell can be lowered to match, cos you need a fair bit more inlet duration & area. I'd suggest aiming for about 170deg duration to start with & adjust to suit from there.



It was a 73 or 74 250 bottom end I measured. From memory the spigot dia in the cases was 85mm I think. Sleeves are commonly 4mm thick, so for a 77mm piston, the sleeve would typically be 85mm dia - & fit right in. I suspect Maico used the same cases for 250 & 400 radialfin engines in those days. But I don't have any of these things in front of me to check.

You'd need to check everything yourself before you started.

Done properly, I have no doubt that a 326 engine would be a sweet engine, as BigK & Firko indicate on the old posting. I would think it would be even better w the radialfin engine like BigK's than in the factory-done squarebarrel engine.  (No offence Mark, just a later design)

Later 320 Maicos actually used a 76mm piston, not 77, but its close. Those 320's were said to be very fast too.

[paul]

i think keith stacker built that engine  from memory   

[JC]

Can anyone check what he did? (If he gives away his secrets)

My guess is he started w a blank sleeve.

[paul]

isinit all ready on this post /or the original post . and it not there i remember asking him last time so when i go over there this week i will ask again ,

[Hoony]

if you See Keith Stacker Paul, ask if he ever put a Honda top end (4 stroke) on a Maico bottom end? someone once told me this years ago but i think it may have been a myth as thats a lot of engineering to run cam gear, oil feeds  etc.

[paul]

well i will ask him but if he burst out laughing  and calls me a idiot   i know  ive been set up a beauty  .but any thing is possable

[Hoony]

it was probably more likely a honda engine transplant into a Maico frame i reckon as thats possible.

[JC]

Paul,

I think the last 326 post in Jan ended w you saying you were going over to stackers & would ask, but I don't think the answer was ever posted.

[paul]

mmmmmmmm    ok   iwill ask again      sorry im a tad late with the answer

[Rosco400]

Ive got Keiths Stackers or what im told was keiths old 250 square barrell in the shed although havent had the need to pull it down yet, gotta say though its got more pull than my 77 AW400 so will be interesting to see what has been done when i get a chance to pull the top off at the end of this season, (although i aint telling anyone ) Kieth Stackers old 400 square barrel was for sale on ebay a while back as well when i bought the 250 and didnt get a bid at 5200 off memory and it was immacualte and had been ported etc by keiths son so i was told, bloke who was selling the bike was bloke from Victoria named Alan and sure he still has it, it would be one nice bike to get a hold of


Sorry that was a bit off topic, just felt the need to say it

[holeshot buddy]

hoony, keith did graft a honda topend
onto a maico bottom end
and keith makes all the sleeves  he can do them from scratch
but i am not sure if he is still doing them
and i dont think paul is doing them  
paul can ask and get back to us



and he did transplant a honda engine in a maico frame
it was his trail bike

[paul]

holeshot, keith is still doing sleeves  he did one for my mega 2