Nearly all diesel buses are subject to the Clean Truck Check.

[Gary Hatt - Publisher BCM]

Here are the latest rules for operating heavy equipment and buses in California.

In general, California registered motorhomes and California registered agricultural vehicles will be required to test annually on a schedule that aligns with each vehicle's DMV registration expiration day. However, for 2024 only, compliance deadlines for all vehicles will be extended to the second half of the year to provide vehicle owners with added time to determine which compliance testing option best meets their needs.

https://ww2.arb.ca.gov/resources/documents/guidance-vehicle-owners-2024-periodic-testing-requirements-vehicles-subject-0?fbclid=IwAR30P45OTb3yTOHVwZHQulD15e_ZdYiu1un7d1XbYPsxLcocqRwaAN30PT8

[windtrader]

Thanks for posting here. I've been following this for some time and am happy to share my experience with the process.
My personal interpretation is most of we California resident busnuts with older 2 stroke diesel engines are affected by the new regulations. Previously a bus converted to an RV was titled as a motorhome/housecar and exempt from CARB smog regulations.

Two steps are important. First, you need to register with CARB and add your details to the database. The deadline is end of this year.
Second step is compliance which requires a smog test that is submitted to DMV to renew registration. As stated, those with tags expiring in the first half of the year get extra time but after that time, the valid test is required at time of registration renewal.
FYI - I wanted to know if my bus was going to pass; it does as confirmed via opacity test performed a few months ago.

[luvrbus]

People are dreaming about 2 strokes living in CA ,CARB will get you the next time around there is no way they will allow the most emission omitting engine ever made to keep running on the roads in CA. My friend that owns a testing center in Needles says all it is going to take is some body in a new EV to call about smoke and they will pull you over. 
Bus owners went through this crap with CA with 45 ft buses they made you truck 45  ft buses across CA that were legal in every state for a few years till the feds said no you can control a state highway but not a federal highway

[Dave5Cs]

CARB didn't know much about them and didn't care until someone shock the Beehive, Just sayin.

[luvrbus]

CARB didn't know much about them and didn't care until someone shock the Beehive, Just sayin.

CARB  has been after the 2 strokes since the early 80"s or mid 70's DD did everything possible to please that group. Don Fairchild worked for years and every time he would get close they would raise the bar, he finally threw in the towel and called it quits at Teir 1 ,there are more friendly states for 2 strokes than CA ,  AZ in some counties are testing those for emissions now ,if they don't have the original emission  sticker for the year made they won't register a older bus it sucks here Mohave County they don't care but I look for that to change

[Dave5Cs]

They didn't care about old RV bus conversion it was only trucks in Commercial service and especially fleets in 2010. Then someone let them know all about Bus conversion and now they will start little by little working to stop them too. I no longer care I don't live there anymore and don't really care just funny how it happened.

[dtcerrato]

Is human smoking allowed in California? 

[Dave5Cs]

@ Dan  What is Human Smoking? only outside and  around state and federal buildings..... Oh ya of all kinds of other things, LOL

[luvrbus]

@ Dan  What is Human Smoking? only outside and  around state and federal buildings..... Oh ya of all kinds of other things, LOL

CARB is bad news to owners but they have cleaned diesel engines up with all their rules  you see the newer trucks on the road the exhaust stacks are so clean they look polished and never a puff of black smoke from one now .I am still trying figure out what part the funny looking tips on the stack plays in emissions.

[windtrader]

the frustration is absolutely understood and well deserved and the historical trend has not been good for 2 stroke engines in CA. CARB has for all practical purposes hunted down and killed all vehicle 2 strokes and well on their way to killing them off on smaller garden equipment. I believe this round sweeps the ag vehicles and other off road, standing machines.

Might there be one final stab to vaporize what's left, who knows? I've not actually done an inventory of what is still legal. Clifford and other knowledgeable mechanics know better how much visual opacity there is at the 5% limit. I took mine in to get tested. CARB rules  specify the J1667 standard device for the smoke/opacity testing. It's the same as has been in place for years.

Personally, I sleep well this go around as mine tested at 1.5%. It is an accelerator or snap test so it will fail any engine that emits much visible smoke when under hard acceleration.

Now, those that fail have one more path which from my research should protect them for the long term. These buses are old enough to qualify for historical vehicle classification. You need a current title to convert but once you do it will fall into the category of all motor vehicles made from the beginning of time. There are some restrictions on use but it's not anything we need to worry about as nobody uses their bus conversions as daily drivers.
Long story short, if you got a clean engine, don't worry. If you fail, get it titled as historic.
What I still find amazing is the lack of comments from others impacted. Maybe I'm the lone bus conversion owner left in CA? lol

[Dave5Cs]

Clifford do you go to the state line to breathe clean air because you know it stops at Arizona. It can't leave the state LOL

[dtcerrato]

Clifford do you go to the state line to breathe clean air because you know it stops at Arizona. It can't leave the state LOL

Back a few decades when California's smog was a lot worse - meteorological data showed that the air quality at the Grand Canyon was obscured 158 days per year caused by LA basin smog. So I doubt if Clifford found better air at the state line. Lol

[luvrbus]

Back a few decades when California's smog was a lot worse - meteorological data showed that the air quality at the Grand Canyon was obscured 158 days per year caused by LA basin smog. So I doubt if Clifford found better air at the state line. Lol

We get a lot of bad air from CA when they have forest fires,the pot pollution is just when we get wind from the south they grow more pot in Needles than Mexico does. Needles is 1st place I ever saw where you charge your EV buy pot and smoke it in a restaurant lol you don't see no smoking signs around that restaurant and no I haven't been to that restaurant but Van and I are going to check the food out oneday   

[Iceni John]

I recently had my engine completely rebuilt after it ate a camshaft, so I assume it's now running as cleanly as it ever can.   The snap opacity test does still worry me:  it didn't take too many miles until my new exhaust tailpipe was completely sooted up inside!   I wonder if I can get an unofficial pre-test now to know if I'll pass the real opacity test in one year's time.   Fortunately my annual registration is due in December, so I should be getting my new registration very soon in the mail to last me until December next year.

Can a fully converted bus be considered a Historical Vehicle in California?   I thought a HV could only be in its original form, i.e. without having been converted or otherwise altered from the original.

John

[luvrbus]

I recently had my engine completely rebuilt after it ate a camshaft, so I assume it's now running as cleanly as it ever can.   The snap opacity test does still worry me:  it didn't take too many miles until my new exhaust tailpipe was completely sooted up inside!   I wonder if I can get an unofficial pre-test now to know if I'll pass the real opacity test in one year's time.   Fortunately my annual registration is due in December, so I should be getting my new registration very soon in the mail to last me until December next year.

Can a fully converted bus be considered a Historical Vehicle in California?   I thought a HV could only be in its original form, i.e. without having been converted or otherwise altered from the original.

John

Don't worry about the snap test they pass those if not totally out of adjustment yours is a  DDEC and turbo they did allow a few seconds for the turbo to spool on non DDEC engines, one can pass a snap test and smoke like a train under a load .Again  don't worry about the snap test the DDEC has you covered it will not give you more fuel than air to burn the fuel (A/R)