Dyno Cams 255 OHV pics (HS40)

125ccCrazy

125ccCrazy

Well-Known Member
#42
#42
cdoublejj said:
is this it? as long as it does not require ultra guides and lifters.... well actually i might not be against that. as long as it can idle and doesn't "slam" in to gear.

is this it?

Tecumseh Dyno Cams Camshafts 356 OHV 5 5 HP U2 Race Engine Karts | eBay

I think i need a every last ounce of power, my frame may not the be lightest nor the heaviest but, it will be streeted
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with the 356 depending on if they ground any off the base circle you will need longer lifters and if all the added lift is on the lobe you will most likely have clearancing issues at either the bottom of the lifter bore, rod, crankshaft, head or all of the above...... that's a huge jump from stock.
 
ole4

ole4

#43
#43
The base circle on the 245 I used was about .010 larger than stock. I am guessing here, but I think they did that so you could set clearance on your old valves.
 
cdoublejj

cdoublejj

Member
#44
#44
125ccCrazy said:
with the 356 depending on if they ground any off the base circle you will need longer lifters and if all the added lift is on the lobe you will most likely have clearancing issues at either the bottom of the lifter bore, rod, crankshaft, head or all of the above...... that's a huge jump from stock.
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what modifications would be needed?

Tecumseh Power said:

hat 356 cam would really need a lot of mods to be used. The cam is designed to have a target (Max) RPM of 9500 and recommended spring pressure (In / Ex): 42 - 44 lbs and recommended timing of 32 - 34 degress BTDC. It would require machining of the head for valve clearance, billet lifters, welding/reinforcing of the lifter bores in the block, and would really need bigger, better valves to take advantage of the cam. You would have run a race clutch that would engage at a high RPM because this cam would make no low end power. Other than drag racing, I cannot see a practical use for this cam on a mini bike.
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I'm wonder how on par that is seeing as the 255 was a bit milder than we thought?
 
125ccCrazy

125ccCrazy

Well-Known Member
#45
#45
I would have to agree with their statement... the 356 is a lot more cam than the other two listed....the 255 may not be a thumper but it will surely be an improvement over a stock cam..if you want a peppier engine the 255 will be a good choice, if you want a hot unlimited engine and can do the work and or afford to build it the 356 will be a good choice..
 
cdoublejj

cdoublejj

Member
#46
#46
125ccCrazy said:
I would have to agree with their statement... the 356 is a lot more cam than the other two listed....the 255 may not be a thumper but it will surely be an improvement over a stock cam..if you want a peppier engine the 255 will be a good choice, if you want a hot unlimited engine and can do the work and or afford to build it the 356 will be a good choice..
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yeah but, is my shit gonna have to rev 4k before it slams my TAV2 "in to gear" or is there a way to handle that? i was thinking i'd red like at like 7500 rpm with a Isky cam but, 9500 RPM is cool. :laugh: lol

I do plan having a bigger than normal mini and not dinky wheel no rake doodle bug, not to knock the old minis (they are good fun).
 
H

Havasu Dave

Moderator
#47
#47
cdoublejj said:
yeah but, is my shit gonna have to rev 4k before it slams my TAV2 "in to gear" or is there a way to handle that? i was thinking i'd red like at like 7500 rpm with a Isky cam but, 9500 RPM is cool. :laugh: lol
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Your TAV will engage at the RPM it always does. (2200 RPM) What you really need are the torque and RPM curves off the dyno. (Don't we all)

The other thing is the fact that at high RPM those belts drag as they attempt to stick in the sheaves.

This is argued here, (I don't care) but Comet does make reference to it. 2200 engagement RPM and 3100 maximum RPM. Sure we exceed that, but doubling the maximum RPM rating seems wasteful, as does burning up belts on a heavy bike at 7000 RPM.

If you want RPM, go with chain. You're planning on a big (heavy) bike with TAV, so RPM isn't your answer. Torque is, at manageable RPM.
 
David wulf

David wulf

#48
#48
Havasu Dave said:
Your TAV will engage at the RPM it always does. (2200 RPM) What you really need are the torque and RPM curves off the dyno. (Don't we all)

The other thing is the fact that at high RPM those belts drag as they attempt to stick in the sheaves.

This is argued here, (I don't care) but Comet does make reference to it. 2200 engagement RPM and 3100 maximum RPM. Sure we exceed that, but doubling the maximum RPM rating seems wasteful, as does burning up belts on a heavy bike at 7000 RPM.

If you want RPM, go with chain. You're planning on a big (heavy) bike with TAV, so RPM isn't your answer. Torque is, at manageable RPM.
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Dave is correct the TAV is useless after about the 5 k range . The Honda Powell I just did for my brother has a opened up GX200 Honda , revs about 5200 and the TAV is at its limits . We also tried one on a 9000 plus Honda and its was a joke , the motor had its way with the TAV . JMHO
 
125ccCrazy

125ccCrazy

Well-Known Member
#49
#49
the cam may be capable of 9500 but without all the goodies and mods it requires to get the maximum performance from it your not going to twist 9500 under a load... if you want power and torque for a big off road bike you may want to contact Isky or Precision cams and see what grind they recommend for your application....
 
cdoublejj

cdoublejj

Member
#50
#50
I ....wonder if i could just trade off the TAV2 since it's still NIB and geta transmission, i remember watching shows there the trans just hooks up the engine via belt or chain, i wonder if i could just find a small trans and get one of those Briggs/Tecumseh clutches that has the trick clutch lever? ...then go crazy on the engine. all assuming i could make good low end torq and do well with a 255 and TAV2 and work with what i have??? (goal of 35+ MPH nothing crazy)
 
cdoublejj

cdoublejj

Member
#52
#52
So then will god drive train and solid engine i'd be approaching hauling ass territory? Either way i'm gonna hot rod it so that is not a waste of money. If you set you exceptions low it's hard to get disappointed.
 
D

davidlamb78

Member
#53
#53
If I remember right, running a tranny will require a certain amount of horsepower (depending on the transmission) just to make it turn, and it may not be worth it. You may end up using too much HP just to make the old HS40 turn the tranny. I'd recommend getting one of those little Honda 250 Rebel engines that have the transmission in them already. They're considered a pooch on the highway when they're in the Rebel frame, but I bet they would do wonders to an off-road mini bike. The old Honda CB, Kawasaki KZ, and all of the old Jap bikes made smaller engine models. The Honda Rebel is a single cylinder engine, and would probably fit with some light modifications. You can probably find the clone version for cheap as well. I think I even saw one on here in the classifieds. Don't get me wrong. I'm sure it's doable. Everything is doable.
 
cdoublejj

cdoublejj

Member
#55
#55
I've already got some Honda engines with a trans already. The HS40 project is pretty much underway anyways. maybe i will just have tim Isky regrind the stock cam. That may be the VERY best bet, I have a head clearance for compression and not RPM, i have a TAV2, do NOT have a full billet fly wheel, maybe i should grind the thing out for for may power at 3600-4k rang and below.

I have an old lawn mower once that had maybe a 7HP engine that had a trans. it was rather small in size. if go that rout that's what i'd look for. It could in theory be possible to make using honda trans from minibike engine. if one 3d printed a casing in ABS plastic and used that as the basis for an aluminum mold. A bit on the extreme and or expensive side though.
 
cdoublejj

cdoublejj

Member
#56
#56
...wait.... my GY6 has a read line of like 9-10K and it has a CVT. maybe it is the way the TAV 2 is set that it does not like above 3600 RPM. on the GY6s you can kits to modified the RPM range on the CVTs. I wonder if the TAV 2 can be modified.
 
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