A12 cam on 1p57
 

Hello everyone I recently purchased a hammerhead gts 150 and I already did some mods to it. Uni intake, straigh shot muffler exhaust, ngk plug and performance coil, 130 main jet ( elevation here is 400ft) . It ran great, toped out at 46mph, it also surprised me on it's ability to climb ( i'm 200lbs), I wanted more power so I (like an idiot) bought a motorio A12 cam and installed it no problem, also p&p the intake manifold, dialed in the valve gapping and put it all together, it started right up but soon after start, it starts to die. I noticed that if I feather the air in by partially blocking the intake it stays running, If i give it gas it revs nicely but at idle it just seems like it needs more gas, like it's sucking too much air, I already ordered a 38 pilot (came with a 35). Now i did more research and found out u cant put a A12 on a 1p57 due to the springs not being able to compress all the way. I quickly went out and checked it out. The springs don't max out on compression and i took the head off and the valves don't seem to have ever hit the piston... The original cam on intake lobe measures 26.3mm the A12 had 27.0mm So I don't see a big difference on the lift. Should I leave the A12 in? And also I thought it couldn't be done on 1p57 heads? The block actually says JL1P57F... Thanks for any help

You may still need a larger idle jet, but did you check yours for blockage? These things can clog if you burp, sneeze or fart. The A12 should still idle (maybe not the best) with the 35, and your symptoms do sound like idle circuit clogging. Next time you have the carb off check to see if all of the Carb's transfer ports are clean, you may have gotten junk in one of them. Spray carb cleaner through the idle circuit and make sure that it comes out of the ports (wear safety glasses). I am unfamiliar with your head a case model numbers, but a check for coil bind and valve to piston clearance will tell you if you are fine.

With the head on, rotate the engine until the cam is at max lift for the intake. Then using a feeler gauge, see how much clearance you have in between each spring coil. Then repeat for the exhaust spring.

For valve to piston clearance, pull the head and spread some room temperature play dough on top of the piston. Put the head and cam back in, then rotate the engine through its complete cycle. Pull the head and examine / measure the indentations made by the valves in the play dough. This will give you valve to piston clearence

Will do!
 

Will do, I am port polishing the head at this time, I saw the ports and they looked like crap. U can see the casting lines (more like steps) where the molds met and a bunch of bumps and rough surfaces, but will do the carb inspection and playdough test. I am actually thinking of just buying a 26mm carb($23+ free shiping) it's exactly like the one that came in mine execpt mine is 24mm. Do you know the cearence measurements for the springs and valve to piston? Thanks for your reply. it is my first post and was a bit bummed as nobody replied. I guess i just had to give it time. Thanks again!

Quick check
 

I went to the garage and checked out the carb, all looks clear I have a fuel filter on it and have ran marine fuel since day one. Maybe its the petcock, I did a major rear remodeling of suspension so it was sitting for about 3 months...

The clearance rule that I go with is kind of a 60 / 100 rule. Typically you want 0.060" clearance between the intake valve and the piston and 0.100" clearance for the exhaust valve. As far as the valve spring, clearance before coil bind, 0.060" is a good number, and you want to make sure that you have around 0.090" of clearance between the valve spring retainer and the top of the valve guide.

Most of my engine building experience has been with the air cooled VWs (30 years) and dirt bikes, and these guidelines have served me well (not for 2 stroke though :D.). The A12 is a fairly mild grind, so if you can get your numbers in these ball parks, you should be fine.

Thanks for your help as soon as I p&p it I will do all the clearence test thanks!

Port polish almost done
 

Had to wait for that 1/4" sanding drum i ordered

This a before pic

After
 

After the sanding but still need more polishing!

Header work
 

Looked at my header and found this inside started to remove it

Hard work
 

Hard to get out but it came out, seem like this inside tube that came out about 1/8 inch went inside the exhaust port, it restricted big time.

Smooth
 

Smoothed out the inside of where the fleange meets the tube, i'll order me a gasket and done on this end

You do not want to polish the intake, only the exhaust runner. You will need to use a flat flange gasket for after removing the exhaust nipple the exhaust will not seal with the traditional round crush gasket.

thanks so much I have them both just sanded smooth and was about to go to the garage and polish them, but curious why not polish the intake as well? I know that polishing is so carbon wont stick all that easy, there is no carbon in the intake I know but wont it flow better polished? thanks for your help and yes I already looked at some flat flange gaskets for the exhaust.

Polishing deters the atomization of the fuel. A rough surface helps atomization and mixing of fuel with air for a more complete burn.

Cool so no polishing for the intake, evn better as it sucks to get in there!, will do the exhast only. Thanks SYCARMS!