Loosing a little power on your MM?

[Converted]

My speed and RPM has dropped off a bit. I'm looking to do some mods anyway but I wanted to see what was causing the trouble. I tied a string to the throttle lever on the carb and ran it WOT in the water. I then pulled on the string to check to see if the governor was set correctly. In my case it was, there was no additional RPM when pulling on the string.

I decided to do a compression check. #1 had 150psi and #2 had 130psi. That's a little out of spec but not terrible. While I had the plugs out I did a leak down test. WOW, both intake valves were leaking so bad that I could not do the test. The #2 intake was really bad (hissing air out the carb). I'm actually surprised that it is running as good as it is with the poor sealing valves.

I'm going to go ahead and pull the heads and do a 3-angle valve job. I'll also have the valves back cut for better flow while they're out. I'm going to shave .050 off the heads and port and polish them as well.

I'll post up pics and instructions for the whole process. I'll also post performance numbers to see if it does any good.

I have the dual exhaust on the way and a loaner big blade prop to use for testing. I'm going to go with the new 3 blade which should be out this summer. I haven't decided on a carb kit yet. I'm going to port the intake and see if the stock carb can be tweeked a bit first.

:tongue1:

[Kevin Hall]

I'm planning on doing mine ... after it's out of warranty.

The leaking valve could be responsible for the lower compression on the #2 cylinder.

The stock intake and carb can be tweaked quite a bit .... blend the intake runners right behind the carb & smooth out the flow. The carb will need bigger jets ... 148/154 seems to be the standard "stock" jets.

As far as aftermarket carbs & intakes .... Extreme V Twins (EVT) in Texas makes a killer intake ... coupled with a Mikuni carb. It is a lot smoother flowing than the BPS/MB intake & adapters.

[whistlingwings]

David, you had the engine at TDC during the leakdown correct?

[Converted]

No I had it in the middle of the intake stroke :occasion14

Ha ha, Yes TDC

Hey do you have a Neway valve seat cutter? I'm thinking about getting the Lawn N Garden set. It has a 45 and a 15/60 plus a few guides and the T-handle.

[whistlingwings]

I ask because its very easy to be an RCH off of TDC.

Neway, no, I do have the briggs factory service Kit.

[Converted]

Is the Briggs kit cutters or stones? Does it have the 15/60? I called Briggs and the folks on the phone were slightly less than useless.


Here's the big question... Can I rent it for a couple days, I'll pay shipping both ways!

[whistlingwings]

They're all cutter type in my kit, 31/46 for OHV twins is what Briggs supplied me.

The 15/60 is normally used for non OHV applications.