Suzuki GSX-R Motorcycle Forums Gixxer.com banner
1 - 5 of 5 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
Hello folks. Got the (not quite but getting there) terminal results a bit over a week ago: my k5 750 is losing compression. 149-159 across all four cylinders, bumps up to 175-180 with oil dumped into the cylinder (rings are going). Really no surprises there as we're at about 76k on the motor, and she doesn't see anything but hard weekend mountain rides and track time these days.

Anywho, my buddy swears that running leaded race gas restored (at least somewhat) the compression in his ailing rc51, which he put down to the lead depositing onto the cylinder walls and piston rings. Sounds like snake oil to me, but I'm going to run u4.4 my next track day if I can get my hands on some, and I'm wondering if it wouldn't hurt to run some lead additive in the pump gas in the meantime. I've looked around and not found a damn thing to back up my buddy's claim, so I just thought that I'd throw it out there to see if anyone agrees with him. Closest that I found were people backing up an oil additive called Restore that contains lead (among many other things) that supposedly restores compression. My baby isn't quite sick enough for me to dive off the deep end trying that though.

Been getting a lot faster this past year (is that why the bike feels slower? Eh, think not). She won't go faster than 130 before turn one at laguna, maxes out at 160 on the freeway and I'm pissed about that. It's possible that there are other things holding her back on the top end (like my unsealed ram air) but idk. Anyways, if I do rebuild her, anybody have any good recipes? Curious about cams, etc. Wondering if 165 whp is possible on pump gas.

I probably should just get a good used s1000rr because I'm hoping to race in AFM superstock next year, but really I'm not that fast, so I'd probably be happy giving this old girl some more life chasing faster lap times... thanks for any input.
 

·
Likes to race old junk.
Joined
·
2,403 Posts
When lead was common in pump gas during the 70's and earlier, it was actually intended to help cushion the valves and seats.
There is no "mechanic in a can", if your engine is worn out and needs to be rebuilt, there's no getting around that.
 

·
Premium Member
Joined
·
73,373 Posts
1. Without a Livengood/Carpenter/etc... Superbike build, you aren't gonna see 165rwhp out of a 750. And thise motors need to be refreshed more often than you want to think about.

2. No, leaded gas won't help much.

The motor is tired. Do the right thing and either get it rebuilt, or sell it with full dieclosure and buy a new bike. As a former racer and track day coach myself, I am gonna warn you about starting your racing career on a 1000. I would strongly suggest getting a fully prepped 600 and race with it.
 

·
Captain Obvious ... because obviously it’s obvious
Joined
·
4,065 Posts
If you're not that ultra fast to begin with, just use the engine as it is. It's still more about your skills as a rider at this point compared to making power.
 
1 - 5 of 5 Posts
Top