Seca Turbo gurus (longish post)

My '82 Turbo has the Yamaha Power Upgrade kit and runs great, but I'd like about 3-4 psi more. I don't have a boost gauge, but the kit seems to be installed properly and runs just like a friend's '82 did also with the upgrade. I have an NOS upgrade kit with the instruction sheet so I'm going to recheck the install on my bike just to be sure everything's there. Is there a safe and relatively easy way to get 3-4 more psi??

P.S. I took the bike to the Deal's Gap area recently and couldn't believe how well it did. It has Progressive brand fork springs (stiffer than stock springs; no air pressure needed), tapered roller steering bearings, BT-45 Bridgestones, EBC front brake pads, and a Nissin front brake master cylinder upgrade from Randakk (originally purchased for a '78 Goldwing, but it works great on the Turbo too). Just keep the rpms up and it will jump out of the corners no problem. Also, the bike only has about 7k original miles so everything is still tight. I love this "antique"!

 

STAY ON TOP of your valve clearances.

Initial check was to have been done at 3000 miles and then every 5000 thereafter. If untouched, at 7K you're 4k overdue. Not cool on a Turbo motor.

Tight valve + turbo on boost = not good result.

"Original" doesn't always mean "good to go." My 550 Seca only had 7100 original, untouched miles on it when I got it. And 7 out of 8 valves were tight.

 

Will do ASAP.

 

I had less than 7000 miles when I started restoring it, and 7 of 8 valves were tight. Take bigfitz's advice.

As far as increasing boost, you can with an manual boost controller. I've heard of people running 18 psi of boost "with out issue" and even higher, but that doesn't mean that I recommend doing it or that any means was used to "verify" that there weren't any issues.

The most important thing to understand is that the carbs are pressurized by the fuel pump to maintain a 2psi differential between boost pressure and fuel pressure. Otherwise you can't fill the bowls with fuel and you lean out the mixture (until you run out)

The power up kit was limited to 12psi, because the rating of the fuel pump was 14 psi. So you'll need a higher pressure fuel pump.

You also have to shim the blow-off valve in your surge tank so that is does not pop before the waste-gate opens. That will require some calculations regarding current preload vs the preload you want to determine how much to shim.

You definitely want to run a boost gauge so you can verify that your manual boost controller is opening at the correct pressures and not over boosting your engine. At some point, they do blow up.

 

How tight (in general)?

Any recommendations for a suitable boost gauge??

 

Out of spec is out of spec. In my case there were two that needed "two sizes down" on the shim to bring them in spec.

But like I said, out of spec is out of spec, especially at 10K rpm. ESPECIALLY under boost.

The most important valve clearance check was the FIRST ONE, which was often ignored. That's why it was spec'd at 3K miles; but nobody ever took the bike back to the dealer. A lot of these bikes were onto their second owner when they hit 3K miles. And unless a true enthusiast had his hands on it in the interim, chances are yours are untouched too.

Here's how to check and adjust them: http://xjbikes.com/Forums/viewtopic/t=14827.html

Part Deux: http://xjbikes.com/Forums/viewtopic/t=29209.html

Don't blow up that pristine motor by ignoring simple maintenance.

Plus, if you've got a few tight valves now and you bring them all into spec, you will feel a NOTICEABLE increase in torque and horsepower throughout the rev range, especially as the RPMs rise.

 

All you need to know really. The turbo motor is going to be harder on it's valves under boost so even less tolerant to them being out of spec.

As for the boost gauge, pretty much your choice really there's loads on the market. I'd go for one that measures In/Hg vacuum as well as Lb/In boost, and pick one that reads up to say, 5-10psi more than the maximum boost you plan to run so you can see if you're overboosting. Apart from that, take your pick what brand/shape/style etc suits your tastes.

 

Thanks for the info dudes. I have a motorcycle repair business, but I still like to do the work on my personal bikes. Valves are first on the agenda.