Hi all - I'll post the full engine specs up here. I need to double check a few things but what I do know is: Carb - Dellorto phbp 21mm #85 main jet. Reeds - standard that came with the bike. Pipe - BDK Cylinder - Tuned Autisa 93cc (54.5mm bore) Ignition curve - BDK - bdkraceeng.co.uk/tc/products.php?197&cPath=6_67_19 Comp Ratio - geometric: 11:1 and Trapped: 5.92:1 Squish gap - .8 mm Port Timing - Exh: 196.7 deg duration Tx A: 139.3 Tx B: 137.7 Boost: 135.9
Our 50 Jeff Douglas tune was 0.4 I think if my memory serves me correctly. The cylinder must be squared up in a mandrel too allow for the tight tolerance so every time you release the head we would usually a pice of solder and check it in 3 places just to be sure
Building an am6 now. 45mm stroker crank with 50mm bore for 88cc. Vforce reed block and a 26mm smart carb. Can't wait to get it finished! Cylinder manufacturer says 27hp is easy
Enjoying the build, just incase your not aware the later Ar80 cranks have a full size woodruff key in rather than the small pin, I've memories of them smaller pins shearing off from my teen years!
Cheers Mark - pleased you are enjoying and thanks for the tip about the later AR 80 cranks. I did wonder about milling a key slot in to the crank. Makes sense then that the magneto had been moving.
@@AutoBeta2T think I had to trim the sides down. Carnt remember if I had to redrill the holes. That was in 1992. I used to run 16 34 gearing castrol a545, b10egv, micron pipe, kc100 clutch, standard ignition clocked at 75. Always wondered if a honda vision cdi would work .
i had a honda mb5 years ago,bored it to 60cc using a yamaha piston,,38mm mikuni card reed block from a 125 rm suzuki,exahaust port was raised 10mm,bloody timing used to retart about 15 deg at 6000 rpm,did 75mph but 16mpg and 1000 miles before big ends needed replacing,was fun tho at 16,im 56 now lol.
Hi, yes, good point and I agree it is too small. It came with the BDK bits I bought. Hopefully it will show what gains a bigger carb can give... Dat2T recons 29mm carb min for the power required. I do have a 30mm carb to try at some point. Hopefully after I get the bigger reeds fitted.
Hi Rory - it's on the 21mm Mikuni that came with the barrel and pipe I bought. I'm going to make an adapter so I can run it with the bigger reeds and the 30mm carb. It was also on the standard reeds so pretty good? And thank you - I'm pleased you are enjoying the vids ☺️
I used to run RD250 LCs with 20 - 25 thou squish at similar rpm with no piston / head contact problems. Standard bore 54, stroke 54 which I'm guessing is longer than yours
Hi mate - thanks for that. I've never tried that tight but I'll give it a go when I get to head work. I've heard a rule of thumb is 1% of stroke so your spec looks bob-on. I'm looking at around 16 thou (.41 mm) then ☺️
@@AutoBeta2Tjennings or bell said for those small engines it should be minimum 0.6mm but it all depends on everything.... (just two stroke things ehh) i run 0.7mm on my 70cc bike but still squish is not meant to be just as small as possible since its the element of the tuning Good luck!
Hi John - it's the 21mm Dellorto carb that came with the pipe and 93cc kit. I'm going to produce a spec sheet that I'll be able to post up before each run in future vids ☺️
I think it is time for a bigger carb 28 to 30 mm I would try a kx80 carb I bet it would be mental and have you seen that company that sell exhausts and up market CDI that is matched to the exhaust the name is something fire brand the guy is ar80 mad check out
Just a KE100 basket and the extra plate. I need some stronger springs as I did get a bit of slip on the last run... Sorted by slackening the clutch cable a bit but I imagine with more power it'll start again.
@@AutoBeta2T 5 plates is 1 more than standard 4 plate ar80 clutch and 2 more than the standard 3 plate ar50 clutch. The clutches are very weak, we normally fit a kx60 clutch or use specially made thinner clutch plates that allows a 4 plate to become a 5 plate or a 5 plate to become a 6 plate.
th-cam.com/video/Oc6kdjuU1Bg/w-d-xo.html I found this old video of a really fast AR of mine, it would have done 100mph I'm sure , obviously never on public roads though and it was not breaking speed limit in this video.
Hi all - I'll post the full engine specs up here. I need to double check a few things but what I do know is:
Carb - Dellorto phbp 21mm #85 main jet.
Reeds - standard that came with the bike.
Pipe - BDK
Cylinder - Tuned Autisa 93cc (54.5mm bore)
Ignition curve - BDK - bdkraceeng.co.uk/tc/products.php?197&cPath=6_67_19
Comp Ratio - geometric: 11:1 and Trapped: 5.92:1
Squish gap - .8 mm
Port Timing -
Exh: 196.7 deg duration
Tx A: 139.3
Tx B: 137.7
Boost: 135.9
Our 50 Jeff Douglas tune was 0.4 I think if my memory serves me correctly. The cylinder must be squared up in a mandrel too allow for the tight tolerance so every time you release the head we would usually a pice of solder and check it in 3 places just to be sure
Cheers for the info Stephen. I need to deck the barrel at some point so I'll ensure its square then. I've heard Jeff's ARs were quick!
@tke7mu0u The specs are here.., WOndering if the @ thingy works too @ :)
These ideas are so much up my alley you can’t believe it! 😍
Think you are giving me some motivation back to tinker a bit. 👍
Cool - pleased it's providing some inspiration and motivation. This challenge has gotten me focused again too.
Awesome, can't wait for your next mods and dyno runs. Good work 👍
Cheers - me either, just time... Bigger reeds next time which will mean quite a bit of machining to fit. Hopefully another few Hp 😃
Great stuff Dave👍....fantastic to have your own dyno, would love one!
Cheers Marcus 😊 and yes it helps having a Dyno!
Building an am6 now. 45mm stroker crank with 50mm bore for 88cc. Vforce reed block and a 26mm smart carb. Can't wait to get it finished! Cylinder manufacturer says 27hp is easy
Sounds like great build. It will be quick with 27hp! There are some great kits for the AM6.
Enjoying the build, just incase your not aware the later Ar80 cranks have a full size woodruff key in rather than the small pin, I've memories of them smaller pins shearing off from my teen years!
Cheers Mark - pleased you are enjoying and thanks for the tip about the later AR 80 cranks. I did wonder about milling a key slot in to the crank. Makes sense then that the magneto had been moving.
Loving it 🤘🏻
Cheers Jim 😊
I used a yamaha 525 manifold rubber which I think is off a ty175. and a mbx125 carb on a ar I did.
Cool. Did it fit the standard bolt pattern?
@@AutoBeta2T think I had to trim the sides down. Carnt remember if I had to redrill the holes. That was in 1992. I used to run 16 34 gearing castrol a545, b10egv, micron pipe, kc100 clutch, standard ignition clocked at 75. Always wondered if a honda vision cdi would work .
That's a while ago then. If it's any consolation I had my AR in 1993 and it had a load done to it but I can't remember now 🥺
i had a honda mb5 years ago,bored it to 60cc using a yamaha piston,,38mm mikuni card reed block from a 125 rm suzuki,exahaust port was raised 10mm,bloody timing used to retart about 15 deg at 6000 rpm,did 75mph but 16mpg and 1000 miles before big ends needed replacing,was fun tho at 16,im 56 now lol.
Haha Paul - sounds like you had a missile! Fun times - I used to love bezzing around aged 16!
21mm is pretty small for 13+ hp and 93cc, i bet ud get alot more performance from a 26 or a 28 as long as the rest of the intake doesnt restrict it.
Hi, yes, good point and I agree it is too small. It came with the BDK bits I bought. Hopefully it will show what gains a bigger carb can give... Dat2T recons 29mm carb min for the power required. I do have a 30mm carb to try at some point. Hopefully after I get the bigger reeds fitted.
I think you are write he needs bigger carb what about a kx 80 carb or slightly smaller
I love this model, it's great under100cc mini sport bike.
Very nice guy.
I'v it too on my youtube chanel.
You'r bike it my idol.
Cool - that makes two of us that like this model. It had/has a big following in the UK. I'll check your channel out. Cheers 🙂
Is this with the new fitted polini carb and also the pipe could be holding it back. love the vids btw.
Hi Rory - it's on the 21mm Mikuni that came with the barrel and pipe I bought. I'm going to make an adapter so I can run it with the bigger reeds and the 30mm carb.
It was also on the standard reeds so pretty good?
And thank you - I'm pleased you are enjoying the vids ☺️
I used to run RD250 LCs with 20 - 25 thou squish at similar rpm with no piston / head contact problems. Standard bore 54, stroke 54 which I'm guessing is longer than yours
Hi mate - thanks for that. I've never tried that tight but I'll give it a go when I get to head work. I've heard a rule of thumb is 1% of stroke so your spec looks bob-on. I'm looking at around 16 thou (.41 mm) then ☺️
@@AutoBeta2Tjennings or bell said for those small engines it should be minimum 0.6mm but it all depends on everything.... (just two stroke things ehh) i run 0.7mm on my 70cc bike but still squish is not meant to be just as small as possible since its the element of the tuning
Good luck!
Cheers - hopefully I will find the squish it likes. I still think my ignition isn't working as well.as it could which may have affected the results.
That's a very docile squish band is it standard 80
Hi Stephen - yes it is... I just left it as it was. The plan is to go to 1% of stroke so about 0.4mm 🙂
Are these runs on the standard carb, or the new one which arrived?
Hi John - it's the 21mm Dellorto carb that came with the pipe and 93cc kit.
I'm going to produce a spec sheet that I'll be able to post up before each run in future vids ☺️
I think it is time for a bigger carb 28 to 30 mm I would try a kx80 carb I bet it would be mental and have you seen that company that sell exhausts and up market CDI that is matched to the exhaust the name is something fire brand the guy is ar80 mad check out
Hi Lee - I think you are on about Firepower Engineering pipe and CDI?
Have you done anything to the clutch?
Just a KE100 basket and the extra plate. I need some stronger springs as I did get a bit of slip on the last run... Sorted by slackening the clutch cable a bit but I imagine with more power it'll start again.
@@AutoBeta2T how many plates in total?
One more than standard. I think that's 5 bit it's a few years since I did the mod.
@@AutoBeta2T 5 plates is 1 more than standard 4 plate ar80 clutch and 2 more than the standard 3 plate ar50 clutch. The clutches are very weak, we normally fit a kx60 clutch or use specially made thinner clutch plates that allows a 4 plate to become a 5 plate or a 5 plate to become a 6 plate.
Hmmm... I think I need to strip the clutch down and double check. Cheers for the tips ☺️
th-cam.com/video/Oc6kdjuU1Bg/w-d-xo.html I found this old video of a really fast AR of mine, it would have done 100mph I'm sure , obviously never on public roads though and it was not breaking speed limit in this video.
Sounds good. The AR 80s certainly seem to tune well! Sounds great.
lowering the ports is exactly the oposit of what you should do,raise them and skim the head to get the dynamic compression back!
Hi Paul - the ports are already what is consider too high at 140 degrees duration. Also high transfers eat into the exhaust blowdown time area. :)