Camshaft or Big Bore - Which one to go with?
 

Gents,

I'm looking for another mod for my 150 carbide. I'm thinking either camshaft, or big bore kit.

Opinions?

Camshaft seems like an easier install, and if I go that route, I'm not sure which one to go with. A11 or A12. I do mostly forest trail riding so I'm looking for more low to mid range power.

Big bore seems like a big job, but is it worth it?

The big bore is worth it, but wait till you need to pull the cylinder first, it won't be long knowing these GY6 engines. Go with the A12 cam for low end grunt. The cam, IMO, is more bang for your buck. Be sure to mod the CVT to match the power curve with the cam change

From what I have read and info I have gathered from others A12 is well worth it.
The BBK I am getting ready to purcase is a no bore kit, which includes larger valve head and a12 cam too.
The 58.5 will bring you to 155cc. The 59mm (also a no bore crank case) will bring you up to 160cc but I hear the cylinder walls are very thin and no room to increase if needed in future.

I have already disassembled mine and it is a cake walk.
http://www.youtube.com/watch?v=9eZ8SIDyyuY
here is a simple video to follow with.
FYI, no need to remove motor, just seats.

Also from what I gather a12 gives that low end but doesn't take away top end.

Ok, so camshaft upgrade it is. I got a response back from Mike over at **** and he suggests the A11 for good bottom end without effecting top end too much.

https://www.buggypartsnw.com/index.p...nd-engine.html

I wonder what comes stock....

That's exactly what I was thinking.... So I can compare.

I am running the A12 in my buggy and love it. It increased the low end a lot but did nothing for the higher revs.
My son in law went with the A11 and go more midrange and high end, but not much on the low end.
To get the most out of your cam you will want to change the clutch setup and you will also need to change the jetting of your carb. Just doing this made my buggy into a little power house.
One other thing, I also lowered the gearing.
I saw your mods. The cam and the gearing change will make yours like mine. You will love it.

I don't really know about cams but I think you will have to change out ur valve springs depending wich size you get. Just a heads up when you order ur cam.

I don't think you have to change your valve springs Eddie. I could be wrong, but haven't heard if that thus far.

Jimmy, thanks for the first-hand details. Exactly what I was looking for. A12 camshaft it is.

changing with an A12 cam will not require springs, unless you have a racing CDI with no rev limiter, then you would want to bump up to a higher spring rate to keep the valves from floating. Unless you were to swap out the cam with some insane high lift cam like Tom was messing with for the 150's, then head work is not needed. In that case, he actually needed to cut down the valve guides to accommodate the big lift cam.

Hmm, I do have the racing "No limit" coil. So I'll have to talk to Tom about springs.

Thanks!

The big bore alone will not produce more power. Your power will be made through the cam, head and carburation. Depending on the terrain you will be driving will dictate which cam to use. The A-12 with a performance ported and polished head would be the best if you have hills or sandy loose soil.

I put the A12 in both our buggies and they work great. A lot more lift and duration over stock just by looking at the cams side by side. I put new ncy11k rpm springs just to be safe because both motors have about 4 riding seasons on them. The top end didn't gain much but better low end and mid range. My red 155cc buggy has better top end than the 183cc due to the heavier piston and longer stroke.

As for big bores the next motor I do will be a 60mm and a 3mm crank kit. The 62mm piston is cool but the boring was not worth the gain and it has more vibration due to the larger piston and runs hot. I bought the ncy boring tool for $120.00 plus $25.00 shipping.
Not the most accurate bore but it worked. If you go with the 60mm piston you can grind the case by hand but it will be shade tree.
The main thing is to get a piston kit with a side wall at least 1.25mm thick as far as I am concerned. The srp 155 kit in my buggy has a thin .90mm side wall and the 62mm srp kit in my wifes buggy has a 1.35mm. The stock cylinder is almost 2mm thick on my last engine.

This is all my own opinion with the results I have come up with over the years. But I will say you get what you pay for and I got a bad 62mm srp kit with a crooked piston pin bore and was able to get another piston to fix it.

Stick with the Taiwan parts for sure.

Go with a camshaft hands down first and play with some cvt mods if u haven't yet then go into the engine build after those mods

im curious did u try a oil cooler for the 62mm bore? and where u using a synthetic fluid? and what grade weight oil?

No oil cooler yet and I have been using Rotella w15/40 because it is suppose to have more zinc in it to help on cam wear so I have been told.

I bet if u switched to a good synthetic air cooled oil u would see a heat difference if u have a heat gun I would take some temp readings from the case and the head with switching to the oil I just stated compared to what ur using just my 2 cents

I don't think switching oils will keep the temps down. The air cooled oil is just rated at a higher temp before it starts breaking down. I have done research into air cooled engine dynamics, as well as speaking with a few old school VW and Porsche mechanics, and they all say the same thing, air flow. The old air cooled Porsche cars had large louvers to direct air in and out of the engine compartment. I would recommend an oil cooler since you are running out in the desert, but you can get by if you keep the buggy moving. For my application, slow trail riding will not allow adequate flow, so an oil cooler is the preferred fix, as long as there is enough air flowing over the cooler. For this, I am routing the cooler to grab as much air as possible, and also adding a 100 cfm fan to run at all times for slow speed operation.

upgrade the cooling fan maybe?

just a crazy thought i had..................

I don't think there is an upgrade for the fans on the GY6 style engines. Even modding the covers makes the cooling system less effective. You could put a radiator fan aimed at the engine, but the electrical draw would likely hurt performance.

There is an oil cooler for the GY6 which works great in cooling the oil. It uses an adapter which replaces the oil screen plug and has an inline canister to house the screen filter. It's all aluminum. Cost is a bit pricy at $207.00 but as I stated it really works. My oil temp come down almost 50 degrees after some real heavy driving. As Masteryota said you can put a cooling fan on it but the draw will hurt your performance for it puts a load on the stator which will rob you of HP.

I would love to buy a oil cooler but it has been slow at work and money is tight. When I run the 183cc buggy at night it runs awesome or in the early morning. As long as it is in the low 80s it runs fine. I did put a cooling finned heat sink off a Honda blower transistor. I JB welded it to the bottom of the case.

http://www.ebay.com/itm/CIVIC-CRV-EL...#ht_2735wt_807

Yup, looked at that one for my honda, it should work the same, but all I needed was the adapter and it wasn't sold separately.

http://knmparts.com/Fan-Stator-Perfo...rmance-150.htm

http://www.ebay.com/sch/i.html?_saca...or+fan&_sop=15

yer welcome

As Johnny 5 mentioned, if you go with a big bore kit, you want to go with one with a thick cylinder liner. I am an old school VW guy and have been working on air cooled VWs for about 35 years. In an air cooled engine, most of the cooling actually takes place at the head, with a much smaller percentage of cooling occurring at the cylinder. The problem with running a thin cylinder is when they get hot, the cylinder itself will expand. when this occurs the rings can no longer form a good sealing contact with the cylinder and you end up with blow by and a lost of compression. This doesn't do any damage to the engine, but you actually lose power when the engine is hot. Also the combustion squish is more critical in an air cooled engine. Since the head is where most of the cooling is done, keeping you squish numbers low is a big determining factor in engine temperature. If you have a high squish number, more of the combustion will take place in the cylinder and will raise your engine temperature. Also, an oil cooler is always a good idea for a hopped up air cooled engine. Since air is not a good medium for the transfer of heat compared to water, adding an oil cooler will cool the oil and the cooler oil will help to cool the head. I can't tell you what direction will give you the most bang for the buck since I installed my A12 cam and the big bore kit at the same time. At the same time I P&P the head, did the redneck intake and opened up the exhaust. However, I can tell you that unless you make the intake and exhaust more free flowing, you will not see huge results in what ever mod you end up going with.

I ran the stock cam with the 62mmx60.8 stroke 183cc motor and a p&p head that I did myself and got big results with the stock motor. But with the stock cam in the 183cc motor it had no top end only bottom end grunt. After the A12 cam it was night and day performance gain. Just after 30minuets of hard running the power would go away on a hot day. If I let it cool for a hour it would run great until it got hot again. But at night in 60 degree or cooler it runs awesome.

That may be, but seeing as I have not heard of anyone using one, let alone if they are effective, I won't recommend them to anyone. We all know oil coolers work, so thats the next logical step for modded engines. Not to mention, most of those cheap performance parts are nothing more than wallet flushers. Take the race CDI and coils for example, most times people go back to the stock units due to them crapping out or being problem prone shortly after install. There normally is not a cheap and simple fix to the by products of more power. If you want, try out one of those fans, but I remain a skeptic.

I run the 63mm cylinder as does my son and both of us run about 280 psi on the compression either hot or cold. Maybe 5 lbs is lost when engine is hot . The important thing with a thin cylinder is to install one with a steel sleeve and not a cast sleeve. The problem with a 63mm cast sleeve is after time the bottom of the sleeve will start to crack due to the side pressures by the piston especially a short skirt piston. The cast has a larger expansion rate then the steel has if a good quality steel. Also the cast is more prone to crack from its brittleness as compared to a steel sleeve.
The squish area is also called the quench area, or quench band, as it increases the surface area of the combustion area and actually cools or quenches the burning mixture around the edges of the combustion chamber. This assists in maintaining a steady (not violent) burn rate, and offsets any tendency for high speed detonation or pre-ignition to occur. With a low quench area the combustion chamber and cylinder will over heat causing the pre-ignition (violent burn rate in cylinder prior to TDC and plug firing). So the larger the quench the cooler the engine will run. Now if the compression is high this sometimes will also cause pre-ignition due to the heat caused by compression igniting the mixture prior to TDC or plug fire. In this case a higher octane fuel will be needed due to its higher flash point.

i could understand the no name brands not working i would use a koso branded one if i was going to use one

http://www.ebay.com/itm/KOSO-Perform...daa9c7&vxp=mtr


it would be super easy to test with a temp gun and they are an easy install and being down here in miami where a normal temperature is 90+ even now any little bit helps because in reality we have two seasons
hot which lasts for 11 months and kinda cool where it gets cold for a month(btw cold means 50-60)

I feel ya, thats exactly why I have an oil cooler. Less than $30 in it for insurance.

http://royalpurpleconsumer.com/produ.../#.UmMVhEnD-tU

this gives u an idea of what some oils out there can do yes I know our buggy isn't a v-twin engine but the engine is still air cooled just like our gy6 engines are

In retrospect, I think that I should have used the term deck height instead of the squish height. Just curious Tom, what type of deck height do you shoot for when you are setting up your engines?

For the best performance I try to keep it around .025 minimum. With a really erratic cam I will cut deeper reliefs for the valve clearance if case of valve float.

Sleepyrz if you decide to buy that cooling fan let us know if it really cools better than our stock. But start another forum not here. I'm also from miami and that looks like something I can do.lol.... I'm curious and its a cheap way of cooling things down... espesially here in miami. Thanks..... Eddie.