Rochester tab

**Sandaro** · 28-11-2014, 01:46 PM

I recall reading about Trans ams in the early 70's having a tab in the Rochester designed to reduce horsepower for rating and insurance purposes (US equivalent to muscle car scare), but this tab was easily removed and jumped up the power by 25-50 horses.

Was this tab ever fitted to Rochester carb fitted to Aussie cars? If so I'll remove it now. Haha

**HK1837** · 28-11-2014, 03:45 PM

I doubt it, the carbs are too big for a 308 anyway!

**wbute** · 28-11-2014, 04:56 PM

That was the same as the Japanese dirt bike manufacturers method for getting dirt bikes through ADR rules during the 90's. Honda liked to restrict the inlet manifold, (Yamaha used a washer welded in the header pipe as well)and a bung in the muffler with a 10mm hole. Plus a restricter in the airbox inlet. Then geared them to the moon so they were quieter for the ride by noise test. The dealers pulled them all out if you payed extra at delivery.

**Sandaro** · 20-12-2014, 10:44 PM

Hoping someone can give me advice.

Rebuilt my Rochester 4 barrel (ie kit and clean). Runs good driving along but let it sit at idle too long and floods the motor. Had a look and the primary venturies are dribbling fuel at idle. Don't think they are supposed to do this? I presume that at idle via the idle screws fuel is let in below the butterflies of the primary to keep the engine running not as I have seen from the venturies.

I am wondering if anyone knows what the cause is?

**Taily** · 21-12-2014, 03:54 PM

Originally Posted by Sandaro

Hoping someone can give me advice.

Rebuilt my Rochester 4 barrel (ie kit and clean). Runs good driving along but let it sit at idle too long and floods the motor. Had a look and the primary venturies are dribbling fuel at idle. Don't think they are supposed to do this? I presume that at idle via the idle screws fuel is let in below the butterflies of the primary to keep the engine running not as I have seen from the venturies.

I am wondering if anyone knows what the cause is?

Your float level is too high or you have a porous float.

**Sandaro** · 21-12-2014, 07:25 PM

Thanks Taily, at least I now know where to look and hopefully cured.

**Vombil** · 21-12-2014, 07:38 PM

Originally Posted by Sandaro

Hoping someone can give me advice.

Rebuilt my Rochester 4 barrel (ie kit and clean). Runs good driving along but let it sit at idle too long and floods the motor. Had a look and the primary venturies are dribbling fuel at idle. Don't think they are supposed to do this? I presume that at idle via the idle screws fuel is let in below the butterflies of the primary to keep the engine running not as I have seen from the venturies.

I am wondering if anyone knows what the cause is?

crazy! mine has the exact same issue right this minute (i was playing with it yesterday thinking the needle and seat were stuck). the reading ive done suggest float has a hole

**mauser** · 21-12-2014, 08:26 PM

Originally Posted by wbute

That was the same as the Japanese dirt bike manufacturers method for getting dirt bikes through ADR rules during the 90's. Honda liked to restrict the inlet manifold, (Yamaha used a washer welded in the header pipe as well)and a bung in the muffler with a 10mm hole. Plus a restricter in the airbox inlet. Then geared them to the moon so they were quieter for the ride by noise test. The dealers pulled them all out if you payed extra at delivery.

I remember removing those from IT490's when we brought them in the '80s.

Mauser

**wbute** · 21-12-2014, 08:52 PM

Probably should have left them in an IT490 lol.

**mauser** · 22-12-2014, 10:18 AM

Originally Posted by wbute

Probably should have left them in an IT490 lol.

Yep. Always liked my '84 YZ490 the best. Have an '85 YZ490 together and a couple of YZ465G's in bits under the house for later projects. Old MX bikes make great shed jewellery and don't take up too much room. The 465's are matching number cases and frames.... oh and 2 YZ50G and J. Like the biggest and smallest ones in the range.

Mauser