Tecumseh 5hp ohv very hard to start. Knocks a little bit when started

SOURCE: Backfire Tecumseh Generator

To maybe convert your Flamethrower back to a generator, Make sure the fuel line is a good quality thick rubber material (like OEM )since it passes through the engine,HEAT is a issue, if it has been modified to steel, or it's thin rubber, it will overheat the fuel on its way to the carb and cause backfires after the engine warms up , ( vaporizing gas and pressure bypassing the jets flooding the engine) I use 1/4 inch Goodyear sold at Autozone , one of very few name brand quality parts you can get there. The other possible cause is carbon deposits built up on the leading edge of the valve not allowing the valve to close all the way, just clean the valve, it is caused by too lean or rich carb setting or clogged jets, if it is a newer style carb with a pink main jet then debris in this area will always cause backfire, check and make sure the old tiny O-ring on this jet is not still in the bottom of the shaft, people forget to pull them out all the time or give up trying to pull them out, I use a paper clip and bend the end 1/8 of a inch @ 90 degrees to fish hook it out of there, CLEAN THE SHAFT with carb cleaner and a Q-tip.... A Tecumseh engine will always backfire if the carb or airflow is not perfect and sealed tight !!!!!! it looks simple to rebuild the carb but you must take your time and look close, clean it very well, make sure the jet is SEATED properly and all tiny holes are clean, use guitar string not torch head cleaners as they will enlarge the holes and make your carb run rich.

SOURCE: hard to start and backfires from muffler when running

Sounds like the timing may be off or maybethe exhaust valve maybe hanging open.

SOURCE: Briggs and Stratton OHV V-Twin 24hp repetitive valve adjustment

Try pulling out the choke a little, if it stops backfiring the mixture is too lean, check the intake
pipes at the cyl head and also the plastic runners to the carb for leaks.
Dennis in Chicago

Harvey N Tawatao

• 3854 Answers
• Posted on May 22, 2009

SOURCE: Idle seems a bit high. Need to know how to adjust and what RPM

There are a couple of things that come to mind. One is make sure the EGR Valve and intake manifold are not carboned up. I normally have to clean them every 60 to 80,000 miles. It will actually close up with Carbon and restrict air flow and make the EGR valve malfunction. 
Secondly, the diesel pump may just have a lot of wear and it is putting out too much fuel at idle. The only way this can be checked is by the dealer with a VW specific scan tool such as VAG-COM. With this tool, you can go in and look at the the pump timing and start injection quantity. 
I have the start injection quantity many times but you have to have the software and login to get the readings. Most dealers will not do this but would rather sell you a pump if it is off.
Remove the hose from the intake where it connects to the EGR valve and look at the inside with a flashlight. See how much carbon is accumulated. This may not solve this problem but will help with starting and performance issues if corrected.

Good luck and hope this helps. To adjust the Idle, it needs to be programed in to the ECM so i am thinking that it's a Carbon issues that is restricting the air flow which the ECM is compensating to keep the engine from stalling.

SOURCE: 04 crf450.hard start when cold(25deg).kick for 10min.once it

1. First thing is when was the last time you had your valves adjusted
2. On cold start up twist about 15 times on your throttle, as you do that the accelerator pump in carb will shot gas in cylinder, I have a 2003 yx426 & 2005 yz450 have to do to both of them when cold out to get started