Bonneville America Forums Forums Technical Forums General Tech Carbon buildup

Came across some pics of another Bonneville that has some nasty looking buildup after only 15,000 km. He was tearing the engine down to install a Wiseco kit.

In another thread, I'd posted about this Bonneville who had to tear down after losing compression on one cyclinder.

This carbon buildup worries me. Any idea what's causing it, and can the problem be prevented? Is it from the crankcase breather depositing oil in the airbox, which then gets into the intakes? Could it be from crappy gas?

Hey Pat, you still running that aftermarket crankcase breather? I'd be interested in seeing similar pics as above when you do the teardown for the bigbore install.

The first one looks like it might have been run cold a lot, (short trips and never really warmed up) and might have been run with the choke on too long at a time. A bad valve seal could also do it. I notice the owner os from Germany. I'm not sure just when they started requiring cat converters on bikes, but that could be a factor.

Sal Maglie

when i bought my TBA I asked the sales guy what octane shouuld i use. He said don't use premium (93 octane) because
it carbons up the pistons. He said use mid grade(89 octane.) I didn't think much of it at the time and I have been burning premium. but maybe he was right.

Mine told me the opposite, nothing but premium and other guys I've rode with do the same...nothing but.

I've heard different viewpoints on the gas too. One theory says to run a tank of premium every so often because it has better cleaning additives. The manual says to use 89 so that's what I fill up with 95% of the time.

Maybe I'm being paranoid about this carbon buildup, but I haven't seen too many pics of these 790cc twin teardowns. Out of the 4 or 5 I have seen, the two I posted I wasn't happy to see.

FWIW, the bike in the first pics is from a guy that lives in Phoenix, Az. Now the only thing that might be different about that area of the country is the gas. During the winter months they run oxygenated and ethanol additives that promotes a cleaner burn to improve air quality out here.

With cars and electronics, they advise to run the lowest grade that doesn't cause the vehicle to ping. Not sure if that applies to bikes with no electronics? I typically run Medium grade (89 around MD)

Page 9.13 of the manual says 89 or higher. It further states that the bike will run better on unleaded fuel, however; you may try oxgenated fuels not exceeding 10% ethanol. It indicate oxginated fuels could cause problems. I have been using premium fuel. I will have to try 89 next time.

Dave

Over here in merry old England, we have two grades of unleaded, premium & super. The Premium (standard) comes in at 95 ron so I assume(hope) that Triumph have taken any carbon issue into account when building the engine.

Nobby

Sal,
I'll keep ya posted on the carbon I find inside mine. I run 89 all the time.

Could this carbon build-up be part of my 3800-4200 rpm problem with my right cylinder? I think the theory of varnishing on the needle/main jet sounds logical. My bike only has 5000 miles on it, most of which has been short trips on 89 octane fuel.
TM

US gas stations have 2 octanes, or grades, of gasoline: 87 and 91. To get the 89, they mix the two. Usually only the 91 has the new cleaners in it, but some brands (QT, for one) put it in all their grades.

A note about trying to "de-carborize" your engine: some guys have used water, or spray carb cleaner, running it through their motor while reving it up. While this will usually clean the carbon off the back side of intake or exhaust valves, there is a decided risk of getting some of that carbon stamped onto the valve seat, thereby possibly causing a valve to burn. Be careful if you try this!

I use Regular Unleaded gas. I try to come home with a full tank of gas and add a gas additive. Amsoil makes a gas additive called P.I. Performance Improver. One bottle of P.I. Performance Improver can treat up to 160 gallons. So all I do is add a couple of squirts of the additive. Basically one $8.00 bottle can treat about 37 tanks of gas. Obviously I don't add it everytime I gas up, just when I get the bike back home.

The P.I. Performance Improver is great for fuel-injected and carbureted systems. It dissolves and removes fuel system deposits and other contaminants for improved power and overall performance. It will reduce PCV and EGR system deposits and reduces exhaust emissions. It also helps keep the gas stabilized, and helps with keeping the small gas filter from being gummed up.

I travel for work a lot and the bike sits for several weeks (or longer) at a time and this really helps ensure the bike will start when I get back home. When I travel for 3 weeks or more I also drain the carb bowls.

Tom

That is the reason we have a WOT and better fuel..I tore mine down last year for the BB kit..4,000 miles on the clock..clean as a whistle..I burn only BP..premium

Tony

Rotating among major brands of premium gasoline will keep one's engine carbon-free. It must be premium, though, as not all majors put the special blend in the bottom end gas.

Got this info off a web site hosted by an oil company engineer, who did this with his pride & joy Corvette. As I recall, he would change brands about every 5000 miles among 3 major companies.

Sal, here in AZ one can get this good gas at a QT station in all their grades. Exxon-Mobile, Shell and Chevron use it in their premiums, though Chevron may now have it in all their grades, too.

TIP: A way to tell if the gasoline company is selling this newest type of gas is to check their advertising. If they are bragging that their gas meets the new automobile company recommendations, then that's it.

I use Chevron gas most of the time because that's what's on the corner. I do have a beef with Chevron, but it's not their gas. I use a debit card most of the time when I get gas. Chevron won't let you get more than 3 tankfuls a day before it rejects your card at the pump.

I think I'll rotate my brand of gas, and maybe try some Sea Foam