Scott Summer's lower compression tip te510 data point

[Norcalslowpoke]

I recently had the head off of my 07 te 510 to find/correct a bubbles in the radiator (head gasket) problem. While the head was off I took the piston to a local hot rod machine shop to shave 20 thou' off the top to lower the compression a tad, ala Scott Summers.

http://www.dirtbikemagazine.com/ME2...0&tier=3&nid=FE11D727959B4C2AA7906490B9DED4BD

The machinist said that 20 thou is not that much (I have no idea) and that the piston strength is not really compromised. We will see about that after more miles. If it blows up in baja I'll let y'all know.

Thought I'd share my first impressions after getting it all back together and riding it all weekend (Lost Coast Dual Sport Ride, northern CA).

The bike is smoother, starts faster, easier to ride and is significantly less vibey. Seems like it runs cooler too...but I also added Evans and a hi flow water pump.

Power? probably down a tad at high load, high speed, high RPM on the pavement. But I never really use all the power of the 510 in the dirt anyway. Still plenty of power for any dirt riding I do.

It is not as smooth as say a drz400, but is way smoother than stock.

So glad I did this for my needs (dual sport, non racing, non aggressive rider). This combined with the vibranators (save the jokes), & progrip 716's makes for a pretty smooth bike that was kind of a paint shaker prior.

Just thought I'd share.

Scott in Sacramento

 

[ghte]

Thanks for sharing, it was most interesting. Lets us know if there are any longevity issues Scott.

 

[Picklito]

Glad to hear from someone who's actually done it. I thought there were some really good tips in that article.
Even my TE450 runs with such a "thump" that I've wondered if it would be better with a little lower CR.
Did you happen to take before and after compression tests?

 

[OlderHuskyRider]

Thanks for posting this, I am interested in doing it when I get into my top end.
How much did the machine shop charge you to shave the piston dome?

 

[Motosportz]

lower compression... interesting.

 

[waserman]

Is it possible to do the same thing with a thicker head gaskit or base gaskit ? That would eliminate the need to machine the piston while producing the same results.

 

[OlderHuskyRider]

Ye

Is it possible to do the same thing with a thicker head gaskit or base gaskit ? That would eliminate the need to machine the piston while producing the same results.

Yes, Motorhead did it, and I am going to do the 2 base gaskets and the 1.2mm head gasket when I get into my top end for a look-see, I will be de-carboning my head and piston. The resulting increase will not be 20 thou, more like 10 thou, but it should make a small difference, along with a de-carbon job.

MOTORHEAD said: ↑

I'm running two base gaskets and the thickest head gasket right now. I have not posted this work in another thread.​

​

I removed the fitting and installed a screw coated in THREEBOND 1211.​

 

[Norcalslowpoke]

IIRC it was $150 or so to do the piston, and surface the head/cyl surfaces, and check them for cracks/leaks. But it was an old time machine shop in an older, low rent area. Might be more somewhere else.

I thought about using a thicker head gasket/base gasket, but was trying to get the bike ready for a trip last minute and only had a normal head gasket, and the head/cyl were already at the shop.

Plus I figured..good enough for Scott Summers, good enough for me. I just printed the relevant section of the Scott Summers tips and showed it to the machine shop. For my needs, (more dual sport than racing), works great. Hope this helps.

 

[OlderHuskyRider]

IIRC it was $150 or so to do the piston, ....... I just printed the relevant section of the Scott Summers tips and showed it to the machine shop.....

Scott Summers tip #6

The only difference that I'm aware of between the 510 and the 450 is that the 510 has a longer stroke. I chose to ride the 510 this year, simply because I have always liked Open bikes. I'm 42 years old and the 510 has more power than I felt I could use effectively, so Gary Gramer at Holeshot Motorsports machined 20-thousandths [0.020] from the piston dome to reduce the compression ratio. The bike became less of a drag racer and more of a tractor. I believe this mod is responsible for other positive effects that were not so easily noticed, such as even easier starting, cooler operating temperatures, less wear and perhaps even better gas mileage.​

Read more: http://www.dirtrider.com/tech/141_0904_dr_dirt_scott_summers_husqvarna_setup_tips/viewall.html#ixzz1lo9xvFpO​

 

[OlderHuskyRider]

Here's some more Motorhead post from another thread, on his 3 gasket approach to lowering compression:

........., so I just added the second base gasket and the thickest head gasket.......That seems to have gotten me +.018" and a 11.5:1 compression ratio.

 

[MOTORHEAD]

The reason I chose to do the gasket thing with the '08 TE510 is because the piston isn't flat on top, it's concave. Trying to cut .020" out of the bowl shape would have been a pain. Doing the gaskets got me within .002" of what Scott did and you can put it back if you wish.

 

[johnboyhenson]

can anyone tell me what pressure, PSI, i should see when porting a pressure gauge to the spark plug hole. mine's an 07' te 510, and i ran it hot after the left radiator came apart during a race. i'm trying to determine if there's a problem inside before i take it apart.

thanks

john

 

[OlderHuskyRider]

can anyone tell me what pressure, PSI, i should see when porting a pressure gauge to the spark plug hole. mine's an 07' te 510, and i ran it hot after the left radiator came apart during a race. i'm trying to determine if there's a problem inside before i take it apart.

thanks

john

Unless you disable the auto decompressor, you will only see about 135-140 pounds of compression.

Look for the following things to have happened after running a high heat cycle, if you don't see these things happening to your bike, you didnt run as hot as you thought:

Fried water pump seal, coolant gets into the motor oil

Intake manifold boot, the rubber part separates from the metal flange that bolts to the head.

Head bolts gets loose, from the intense heat, everything expands, then the cool down, they get loose.

Rad hoses start leaking

 

[MorrisBetter]

Unless you disable the auto decompressor, you will only see about 135-140 pounds of compression.

Look for the following things to have happened after running a high heat cycle, if you don't see these things happening to your bike, you didnt run as hot as you thought:

Fried water pump seal, coolant gets into the motor oil

Intake manifold boot, the rubber part separates from the metal flange that bolts to the head.

Head bolts gets loose, from the intense heat, everything expands, then the cool down, they get loose.

Rad hoses start leaking

It's info like this that makes this site priceless. The collective wisdom of this site is just amazing. Thanks to all of you gurus that take the time to answer questions, and offer advice.

 

[johnboyhenson]

OlderHusky,

Thanks for the input. I'll check all those things out. I kicked it over on the kickstarter, not using the electric, thinking that the electric was possibly causing the decompression to actuate? However, just using the kickstarter I only see 60psi.....Anyway, like I said, when i get back to the bike i'll check for these signs you mention.

thanks again.

john

 

[OlderHuskyRider]

OlderHusky,

Thanks for the input. I'll check all those things out. I kicked it over on the kickstarter, not using the electric, thinking that the electric was possibly causing the decompression to actuate? However, just using the kickstarter I only see 60psi.....Anyway, like I said, when i get back to the bike i'll check for these signs you mention.

thanks again.

john

Your bike has a 12.9:1 compression ratio, that is about 175 psi compsression, same as my bike. I checked my compression when it was pretty new and I got 135 psi, that when I learned that the mechanical auto decompressor bleeds off some compression so that the starter can work at all.

Electric or kick, makes no difference to the auto decomp.

One way to try and fool the auto decomp into not working is to lean the bike to the far left, even as far as laying it down on the left side, and then try to operate the kick starter. You may find that you will be unable to push the kickstarter thru its travel.

Make sure you are reading the compression gauge correctly, because 60 psi would be a problem with something.

 

[johnboyhenson]

OlderHusky,

Just got back to the bike tonight. Ok, definitely 60 psi. Will not crank. Pulled the Valve cover and i'm in clearance on the intake valves, but neither of the exhaust valves are in spec. (spec is .006 - .008 in.) one will take the .004 feeler and the other will not take the .002 gauge. Also, there was a lot of clattering before it finally gave up. So, now i'm thinking that I might have valve damage and/or piston damage; regardless I'm going to pull the head.

Do you have any advise on who to use to rework the valves, or where to source a set of rings? I'll check with the local Husky dealer, or course, but maybe there's a specialty vendor for just this king of thing?

also, can you point me in the right direction for a shop manual for my bike.

thanks, john