Hitchcocks Forum

Hello all, I recently modified by 1986 Indian Bullet 350cc by replacing the 7.5kg crank with a 12kg. The acceleration has reduced but the ride smoothness and thump is better than the lighter crank. I also removed the Mikarb and replaced with an Amal Monobloc 376. I am having two issues since then,

1. My bike never starts during a cold start with the choke ON. Also, if the bike is warm and running and I pull the choke ON it shuts OFF. With the previous carb it would not do that, it would cold start with the choke ON and during warm idling if the choke was pulled ON its RPM would increase. Not sure why this different reaction.

2. Whenever I cold start the bike, when the bike is idling everything is fine but as soon as I pull the throttle I see white/ bluish smoke coming out the tailpipe. However if I let the bike idle, there won't be smoke. Secondly, when I pull the throttle and the smoke starts coming, if I engage the gear and ride away, the smoke disappears. Completely clueless about this. Also, when I cold start the bike, it would not stay on hence I had to pull the throttle, with the previous carb I would just keep the choke on till the idling stabilized.

Someone suggested this is wet sumping, but if that were the case why does it smoke only when I pull the throttle and disappear when I ride away. I tried parking the bike in TDC, but no luck.

I am very tempted to put the old 7.5kg back in. Help please.

Regards,
Ameya

Leave the crank alone, nothing wrong with it I have done that before, your problem is with the carb, not the crank. You will know when it wet sumps and that is not what is going on at the moment

Hi Ameya, In order to swap the crank, you will have disturbed the top end components and whether you fitted new piston rings or not, you would need to deglaze the cylinder bore to get a good seal at the rings again. Perhaps you did this, but the new, or original rings still need a bit of time to settle in again. The 'choke' on a Mikcarb is actually an enrichener - think of it as a small carb set up for starting and fast idle within the main carb, hence the easy starting and fast idle with no throttle needed. The Amal is a different animal [except the MK II's], where the choke [when fitted] is a separate slide that can be closed to reduce the air intake, causing more fuel to be sucked in for starting, but the tickover will probably not be available and certainly won't be faster - you will have to control warming up with the throttle. If you preferred the Mikcarb's characteristics, refit it, especially as you have fitted a heavier crank, as I am guessing performance is not an issue here? Regards, Paul.

Hello Paul, thank you for the information on the Amal monoblocs.

For the smoking issue, I think all the components are well sealed. I changed the crank when I overhauled the engine to put a new barrel and piston. I forgot to mention that the bike is also gulping oil I went from mid level on the dipstick to barely touching the dipstick in 200 kilometers. There was small leak on the inlet push rod crown which I fixed but I don't think that will drain so much oil.

Thank you,

Ameya

Ameya, the oil loss problem is because your engine is burning it. If you replaced the piston rings they may need time to bed in, especially if they are Indian made which are of poor quality. Did you re-use the original rings and if you removed them did they go back in the right way round and in the same place? Did you re-fit the piston the right way round?
REgards, Mark

Sorry, just re-read your most recent post in which you say you replaced the barrel and piston. I would say this is where the problem is. REgards, Mark

I think the new cylinder piston clearances are correct and the new piston rings are fit in the right way. The mechanic I am talking to is saying that the floating bush in the flywheel has a bigger opening due to which more oil is being supplied to the flywheel, falling down and thus causing more oil being splashed on the inner walls of the cylinder.
I am really convinced by his answer as even if that is true, the scavenge pump is designed to be of a higher capacity than the feed pump.

Sorry, no. If the piston rings are doing their job the oil can't get into the combustion chamber to be burned. REgards, Mark

Not excessive oil consumption gone through probably 400 mls in 200ks, 2ml a k not something to be overly worried about with new rings in a new barrel. Any chance this is an Indian rebuild and if so I will not bother about it anymore. Feed pump can only deliver x amount of oil so I have no idea what the mechanic is talking about getting too much oil through the floating bush unless he has fitted a high cap feed pump and a standard scavenge pump

Thank you Norm. It indeed is an Indian Bullet which has worked fine till it was recently open. I will try to change the piston rings and hope it solves the issue. I have only put royal enfield genuine spares, except the crank.