Hi all, I have a 1700 type 4 in my bus - all standard and OEM carbs have been rebuilt. Fitted with pertronix electronic ignition. It always starts & ticks over fine. I have not checked the timing or the valve gaps since buying it a few months ago. When its cold, it pulls a treat through all gears. However, once up to full operating temperature, it is definitely down on power - it pulls ok(ish) in first and second, but as soon as you are in 3rd, you seem to have to rev it loads to get anywhere, and even then it doesn't seem to pull much. As soon as you get to any kind of hill, it starts to struggle. I realise its not the fastest thing in the world, and they do tend to struggle with the hills, but like I say it's ok when cold, but defo worse when warm. If you floor the accelerator, it doesn't seem to make much difference to just feathering the accelerator. Any ideas? One thing I think it may be worth mentioning - the tube from the crankcase breather box currently goes through the battery tray to underneath the bus, into fresh air - not sure this is correct, as i understand that it should go to the carb? Could this be making a difference, and could anyone supply me with details/photo, of where it should go on the (OEM) carb so I can route it properly. The carbs are OEM but they have been fitted with aftermarket type air filters (like on Weber 34 ICTs) on top of the carb, so no longer using the OEM air filter system. thanx.
It does sound like the engine is running rich either the choke or the usual fuel metering needle valve in one or both carbs.. a bit of dirt caused by rubber breaking loose off the hose during reinstallation of fresh carburettors can be enough. Does it judder very slightly when driving on the flat at 30 mph? Mine does that when the needle valve starts leaking. Your bus should be able to do 70mph and have no trouble reaching 55mph. All buses except hi-tops with "boats" on the roof or the Jurgens conversions really should be able to keep up with the traffic on Birminghams motorways for example
Haha Birmingham’s motorways your lucky to get to 40 mph on any of them so even my 1600sp can keep up lol
Once you get up to speed, it will sit at 60 easy (& more if it were to push it, i'm sure) but takes some time to get there! Piccies as follows: Overall carb set up..(hope you can see in sufficient detail - looks like one image has posted twice for some reason?)..
Update - just took the air cleaners off to take a look at the choke butterflies.. They are opening up fully when the engine warms up, but I did notice that there is a tube behind the left hand carb, which is not connected to anything - if you put your finger over it with the engie running, you can feel a vacuum - piccie as follows - could this be the culprit ? It looks like a tube normally goes from this into the OEM air filter set up, but as i have cone type ait filters (I think that's what you call them!), what do i need to do with this tube?..
On the second pic from the bottom the choke unit looks like it's not fitted correctly, IIRC the flanges should be flush with each other where as yours looks to be sticking out about 5mm. That brass tube normally has a 90° elbow on it that feeds back into the stock air cleaner set up(not got my bus handy to look at so I'm working from my feeble memory).
http://www.itinerant-air-cooled.com/viewtopic.php?t=7767 There's a great write up here about twin Solexes with some useful diagrams though it is biased towards American buses with extra emissions gear
Looks a bit above my technical understanding! Do you mean the choke unit at the front of the LHS carb? Would that cause the loss of power issue? just wondered whether too much air could be getting sucked into the LHS carb through that pipe, which should be connected to the OEM air filter set up?
According to the itinerant aircooled diagrams which even if you don't understand now, that upstanding pipe is the air intake to the idle circuit. It should really be filtered too with a T piece going back into the hose going to the air filter on the left. Its also all described on Page 10 of Fuel System in the Bentley manual, which you can either buy or download. The outside of everything looks clean which is good. Lack of power at speed can be either too much or too little fuel. It can be points closing up with wear and bouncing, worth checking the gap. Or it can be timing not set right or a sticking distributor advance mechanism. Your bus seems like one of those Techenders cases where it runs well enough to get there but will go a lot better after a bit of simple tweaking.
thanks Mike - I will check the timing. Also, will check for leaks, but all the pipes and tubing look recently changed to me. It has Pertronix electronic ignition. I would love someone who knows about type 4 engines/carbs to take a look, but not sure there is anyone close to me & techenders isn't until September I think? the bus is completely usable, but there is somethng missing, power wise.
I live in South Yorkshire,but used a guy when I had problems in Nort Wales, who is based in Chester. I was so impressed, I've travelled back to see him to let him do timing and balance carbs. Worth considering as Chester/ the Wirra is a lovely area to visit.
This is your central idling intake which originally was set up like this: I imagine you could Tee it into the main carb inlet.
I have checked the timing - spot on & advances to 30 degrees at 3k revs. Can;t see any leaks & doubd there are any as all the piping looks virtually brand new or in excellent condition, everywhere. The stock air filter box was supplied with the bus as a spare, so may chuck that back on & see if it cures the problem! Cheers
