11 assualt piston study

Merlin · Jan 2, 2018

SMF & Dave,

Other than the upgraded Bosch injectors, what makes a '12 engine more desirable than an '11?

We didn't get the thicker cylinder skirts until '13......

Just curious?

Sheetmetalfab said:
Don’t get me wrong.

A 12 or newer is worth rebuilding.

Part out the 11’s though............

diamonddave said:
Totally Agree. 11's should all be updated to 2012 or newer.

Merlin · Jan 2, 2018

Well, you've done your due diligence with regard to blueprinting.

If Wiesco calls for a shade under .005" & that's where you're at you've done all you can. That said, running that amount of clearance with forged pistons is going to require proper engine warm ups & a diligent / patient operator.

peaceofwork said:
Off the top of my head I seem to remember the box the Pistons come in said a little less than five thousands 4995 if I recall right. Also for ring gap it specked four thou per inch of bore minimum and I seem to remember
3.35" /85mm eighteen thousands ring gap is what I went with.
The shop that did the renicasiling job had the Pistons before the process began, I mailed the stuff half way across the continent to be serviced so was not their to whitness their measurements but was assured it was at specs. Now after shipping back home I took the monoblock and the piston my local machinist and watched it all get measured out a few times . I know that it's all at least at the minimum spec to a little less than five thousands ptcw

Sheetmetalfab · Jan 2, 2018

Merlin said:
SMF & Dave,

Other than the upgraded Bosch injectors, what makes a '12 engine more desirable than an '11?

We didn't get the thicker cylinder skirts until '13......

Just curious?

Fuji crank.

05rmksteve · Jan 2, 2018

Sheetmetalfab said:
Fuji crank.

Fuji crank wasn't phased in until late builds of the 12s. I've had 3 12s 1 snow check with the mape crank 1 standard season build with the mape and 1 late season build with the fuji. Even some 13 snow checks received the mape cranks.
The 12s did receive a thicker cylinder skirt than th 11s.

peaceofwork · Jan 2, 2018

Merlin , I think maybe by 2012 the fuel map, pump and injectors were figured out better than the earlier models, maybe it's a milestone for cfi factory wizards . I think if you wanted to buy new injectors for a 2011 they're updated to the yellow ones and once installed you then get your ecu reflashed to work in conjunction with the different injectors?
After paying for servicing on the old stock injectors and installing them I learn get new ones because they also come with a new harnes that has been known trouble over the years.

peaceofwork · Jan 2, 2018

I want to be prepared to do a leek down test when I next do the 2+hr drive up to ware the sled is.
If anyone knows the diameter of the big end of the Y pipe and the diameter of the reed intake boots post them up so I could go buy rubber plugs please

Merlin · Jan 2, 2018

That is my understanding of the Mape & Fuji crank usage as well but I don't believe any '12 MY engines received the thicker cylinders.

That came with the '13 MY engines.......

05rmksteve said:
Fuji crank wasn't phased in until late builds of the 12s. I've had 3 12s 1 snow check with the mape crank 1 standard season build with the mape and 1 late season build with the fuji. Even some 13 snow checks received the mape cranks.
The 12s did receive a thicker cylinder skirt than th 11s.

peaceofwork · Jan 2, 2018

Throttle bodies may be 48mm inside diameter but can anyone confirm outside diameter so I could know the size of rubber plugs to buy to plug the reed intake boots ?

XCaSSAULT · Jan 5, 2018

48mm is 1.89” so these 2” rubber caps should work

LoudHandle · Jan 5, 2018

Cap for 1 1/2” pipe is very close to that dimension. 2” pipe is 2 3/8” OD.

gtwitch · Jan 6, 2018

POWork Something I do not see mentioned in this post is the Exhaust valve contacting the piston because the cylinder is worn at the base of the exhaust valve guilotine and this lets the tips of the valve contact the side of the piston (look at the piston for telltale marks). Had this happen on a CFI4 10 800 Dragon and on my own 11 PRO 800 (at about 2700 miles) and have since always machined the exhaust valves (curved end) back .030 to .045 so that no interference occurs. Indy Dan and I talked about this 4 years or so ago and he had seen it and has the tooling to do this but, I have my own tooling to do this set up also. I think this happens more often at 2500 to 5000 miles and when it does it usually destroys the Cylinder and then with a new cylinder there is not a problem. If you have the Cylinder off and can put new (or used) piston into the cyl and then put the exhaust guilotine in, you can see the interference I am talking about!
gtwitch in wyomng

XCaSSAULT · Jan 6, 2018

Would a thicker gasket or doubled up gaskets prevent this valve-piston contact u speak of?

So the valve and the piston must be insanely close from the get go if the cylinder only needs a couple thousandths worn off for the contact to happen?

If piston/cylinder clearance is suppose to be .004-.006 and after 2,500plus miles your in the neighborhood of .008 there could be a contact issue?

This has me interested

LoudHandle · Jan 6, 2018

XCaSSAULT said:
Would a thicker gasket or doubled up gaskets prevent this valve-piston contact u speak of?

So the valve and the piston must be insanely close from the get go if the cylinder only needs a couple thousandths worn off for the contact to happen?

If piston/cylinder clearance is suppose to be .004-.006 and after 2,500plus miles your in the neighborhood of .008 there could be a contact issue?

This has me interested

It is not the cylinder bore that wears. It is the bottom of the exhaust valve counterbore that gets beat on every time the exhaust valve returns to full closed. It eventually compress the aluminum at the bottom of the counterbore. Which results in an increase in exhaust valve travel. I’m pretty sure Indy Specialties had made hardened seats to install into the counterbore to negate that problem (or at least it was discussed). The EV counterbore does need to be machined deeper to allow the hardened seat to be installed though.

gtwitch · Jan 7, 2018

When I talked with Dan about this problem, he was just cutting (Machineing) the large lower end of the valve face with a special cutter he had made to go in his CNC mill when using a jig to hold the valve. I don't get as elaborate and with a caliper in hand I do mine on a belt sander by hand and remove about .040 (give or take) and take the tips/points back even a little more. I've done at least 6 sets of them with no problems or effects to performance. I do have the pistons saved in a box that you can see the interference marks on from the valve coming in contact with the pistons!
gtwitch in wyoming

peaceofwork · Jan 7, 2018

gtwitch said:
POWork Something I do not see mentioned in this post is the Exhaust valve contacting the piston because the cylinder is worn at the base of the exhaust valve guilotine and this lets the tips of the valve contact the side of the piston (look at the piston for telltale marks). Had this happen on a CFI4 10 800 Dragon and on my own 11 PRO 800 (at about 2700 miles) and have since always machined the exhaust valves (curved end) back .030 to .045 so that no interference occurs. Indy Dan and I talked about this 4 years or so ago and he had seen it and has the tooling to do this but, I have my own tooling to do this set up also. I think this happens more often at 2500 to 5000 miles and when it does it usually destroys the Cylinder and then with a new cylinder there is not a problem. If you have the Cylinder off and can put new (or used) piston into the cyl and then put the exhaust guilotine in, you can see the interference I am talking about!
gtwitch in wyomng

Good one gtwitch but I been their and dealt with that, I had called Indy Dan,s shop and asked about PV GUILOTEEN clearance. I was told to put a ring in the cylinder and push it down to the whare the valve starts to enter near the boar then use a 050 fealer gadge to confirm clearance moving the ring down in small increments . I used a sharpie marker then some precision swipes with a Dremmel following the existing angles top side and bottom side of the pv . It took a few repeat and tests but I got it all done on my first wack at fixing this motor,

peaceofwork · Jan 7, 2018

I did mark the power valves right and left and this cylinder was just re nicasilled at the time of pv GUILOTEEN clearancing.

gtwitch · Jan 9, 2018

OK then, I think that we know to fix the Guillotine clearance problem and this interference problem will not be an issue any time in the future! What pistons are you rebuilding with??
gtwitch in wyoming

peaceofwork · Jan 9, 2018

Weisco pro lite forged with coated skirts, clearance checked by two professionals to be a tad more than minimum Weisco specs - call it 5 thou.

peaceofwork · Jan 9, 2018

I believe in 100f before moving the machine at all and no running it hard at all once going for the first while.

gtwitch · Jan 9, 2018

If you have one of the Polaris pistons and one of the Wiesco pistons, look at the ring end closure on both and compare these and then imo this can be a source of problems when using this type of ring end closure in the Polaris cylinder! I now use only pistons that have the Polaris type of ring end closure. I had and can confirm with photos, problems with three sets of pistons with the other type ring end closure to include total cylinder destruction/replacement.
gtwitch in wyoming

11 assualt piston study

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