Vintage BMW Motorcycle Owners

Hello friends,

I am putting the 38mm Hoske silencer on my '84 R80. It runs fine now. After installation do I need to do any rejetting? Thank you!

Welcome to the forum! Not sure if you need to or not, but I would monitor how the bike performs with the new mufflers. Starting, acceleration, gas mileage, plug color, etc. If the performance substantially changes post new mufflers, then you'll need to figure out where the issue might be.

Snowbum has a page on intake/exhaust tuning...this might give you some ideas:

https://bmwmotorcycletech.info/InExTuning.htm

You may want to do what's called a "plug chop". This is done...safely...by running along in top gear at say 60-70 mph and close the throttle and kill the engine while safely coasting to a stop. When it's easy to do, pull each plug out and look at them...if they are very whitish then it's running lean; if they're blackish then running rich. This is all contingent on on what unleaded fuel now does to plugs. In the old days, with all the additives, plug color was a big deal. It might be changed somewhat with the latest fuels.

Probably no need to rejet. The stock BMW mufflers are pretty good flowing.

To be safe do the plug chop as Kurt says. Run the bike at speed (65-70 is good) for at least 5 minutes before shutting down to check the plugs.

Mike