A A A
Avatar

Please consider registering
Guest

Search

— Forum Scope —






— Match —





— Forum Options —





Minimum search word length is 3 characters - maximum search word length is 84 characters

Register Lost password?
sp_Feed sp_PrintTopic sp_TopicIcon
Downhill technique
Avatar
JustinW
Top Gear User
Club Member
Forum Posts: 103
Member Since:
September 22, 2019
sp_UserOfflineSmall Offline
1
December 19, 2019 - 7:55 pm
sp_Permalink sp_Print

What's the preferred method of throttling when going down hill? The bike will go downhill with no throttle, but does this not starve the barrel of lubrication? Do I pull in the clutch and give it a bit of throttle? 

Is engine braking a thing on 2 strokes?

Avatar
NeilB
Kidderminster
Top Gear User
Club Member
Forum Posts: 184
Member Since:
December 10, 2019
sp_UserOfflineSmall Offline
2
December 19, 2019 - 8:04 pm
sp_Permalink sp_Print

You'd have to be going down hill for quite a while with a fully closed throttle to starve the engine, in normal riding this should never be an issue. My first bantam, but not my first two stroke, and never had a problem with "normal" hills.

If you were to find a very long hill, then blipping the throttle with the clutch is would work, but then it's deciding how often and when to do this I guess. 

Avatar
JustinW
Top Gear User
Club Member
Forum Posts: 103
Member Since:
September 22, 2019
sp_UserOfflineSmall Offline
3
December 19, 2019 - 8:27 pm
sp_Permalink sp_Print

I should have said long steep hills. There's a few near me where I'm on the brakes all the way down. I swear the engine actually stops running, at the bottom it almost sounds like it's restarting when I turn up the throttle.

Avatar
cocorico
Central France
Top Gear User
Site Member
Forum Posts: 3313
Member Since:
June 23, 2013
sp_UserOfflineSmall Offline
4
December 19, 2019 - 8:53 pm
sp_Permalink sp_Print

A Bantam has a  robust, low tuned engine. Oil from the fuel mixture is mainly deposited in the crank case to lubricate the bearings, crank and to cool the underside of the piston. There should be more than enough residual oil to carry on that process whilst going downhill. Add to that the fact that with the throttle closed their is no combustion, so only residual heat, which is diminishing from air flow. So no, just carry on riding. Besides, I don't think I have ever seen a road where one rides on a constant throttle for more than a few hundred yards before accelerating or decelerating for bends or other traffic.

1956 D3 running, lights to sort. 7 other bikes in the Barn. 1950 D1 engine being rebuilt (slowly).

Avatar
JustinW
Top Gear User
Club Member
Forum Posts: 103
Member Since:
September 22, 2019
sp_UserOfflineSmall Offline
5
December 19, 2019 - 9:50 pm
sp_Permalink sp_Print

Ok thanks, I'll stop worrying!

Avatar
NeilB
Kidderminster
Top Gear User
Club Member
Forum Posts: 184
Member Since:
December 10, 2019
sp_UserOfflineSmall Offline
6
December 20, 2019 - 8:28 am
sp_Permalink sp_Print

I'd definitely be more worried about cooking your brakes on a long downhill riding the brakes the whole way! 

Avatar
cocorico
Central France
Top Gear User
Site Member
Forum Posts: 3313
Member Since:
June 23, 2013
sp_UserOfflineSmall Offline
7
December 20, 2019 - 10:01 am
sp_Permalink sp_Print

NeilB said
I'd definitely be more worried about cooking your brakes on a long downhill riding the brakes the whole way!   

Quite - in those circumstances, you should be in a lower gear to give some engine braking - which would also do away with your "lack of lubrication" concerns.

1956 D3 running, lights to sort. 7 other bikes in the Barn. 1950 D1 engine being rebuilt (slowly).

Avatar
JustinW
Top Gear User
Club Member
Forum Posts: 103
Member Since:
September 22, 2019
sp_UserOfflineSmall Offline
8
December 20, 2019 - 11:11 am
sp_Permalink sp_Print

I was using 2nd gear to help with braking, this did help, but of course make the revs pick up. But with the throttle closed, I was worrying that no petroil is getting into the cylinder. Maybe it's just not as issue.

Avatar
NeilB
Kidderminster
Top Gear User
Club Member
Forum Posts: 184
Member Since:
December 10, 2019
sp_UserOfflineSmall Offline
9
December 20, 2019 - 2:56 pm
sp_Permalink sp_Print

There will still be vacuum, hence still have fuel going into the engine, just not as much as with the throttle open. It's not like modern fuel injection which actually stops firing with the throttle closed 👍 

Avatar
JustinW
Top Gear User
Club Member
Forum Posts: 103
Member Since:
September 22, 2019
sp_UserOfflineSmall Offline
10
December 21, 2019 - 7:50 am
sp_Permalink sp_Print

Thanks guys. No one seems to be seizing up so no worries.

The next issue will be getting up this damned hill!

I'm 15 stone and it just gets up in first gear. Last time I rode this bike I was a kid half the weight.

It's very happy on the flat but a bit of incline and it needs second. Only the severe inclines require first.

But there's no way I'm going out on main roads, too slow. I always planned to be a back lane bimbler, so I'll stick to that.

I'll be tweaking tte timing and mixture to try to get as much power as possible. Great little bike though, lots of character.

Avatar
cocorico
Central France
Top Gear User
Site Member
Forum Posts: 3313
Member Since:
June 23, 2013
sp_UserOfflineSmall Offline
11
December 21, 2019 - 8:03 am
sp_Permalink sp_Print

JustinW said
... to try to get as much power as possible. Great little bike though, lots of character.  

Have a look at ** Please log in to view **, 'it may be of thome aththithtanthe' to paraphrase Biggus Diccus. wink

Can't argue with the last part of the sentence!

1956 D3 running, lights to sort. 7 other bikes in the Barn. 1950 D1 engine being rebuilt (slowly).

Avatar
SpacedMarine
Up north
Top Gear User
Club Member
Forum Posts: 659
Member Since:
July 1, 2018
sp_UserOfflineSmall Offline
12
December 21, 2019 - 10:45 am
sp_Permalink sp_Print

What sort of bantam are you riding?(forgive me if I missed it) it's just I'm on the large size 6'4 and 19 and change stone and mine pulls my weight up the local hill ok.Maybe have to drop a gear but it does it quite effectively. I found setting the timing correctly made a huge difference between struggling and "flying" up 🤣

What's 7/16 in mm again?

Avatar
JustinW
Top Gear User
Club Member
Forum Posts: 103
Member Since:
September 22, 2019
sp_UserOfflineSmall Offline
13
December 21, 2019 - 11:02 am
sp_Permalink sp_Print

It's a D1, 125cc so I shouldn't expect too much. But encouraging to hear timing can have an effect.

I checked the timing yesterday and it wasn't quite right. I adjusted it so points just opening at 4mm BTDC. As it was set, the points were already open at that point, so that must mean it was too far advanced.

But I haven't attempted 'the hill' yet as its so wet right now. Fingers crossed it might have a bit more grunt.

Avatar
Sponge
Lancashire (A chip shop somewhere near Preston)
Top Gear User
Club Member
Forum Posts: 202
Member Since:
November 6, 2016
sp_UserOfflineSmall Offline
14
December 22, 2019 - 6:21 pm
sp_Permalink sp_Print

I am absolutely huge - and I ride a D1 on a regular basis.  My town is surrounded by hills and everywhere I go seems to be uphill but the D1 copes quite well.  I have found that getting the timing right makes a big difference on a D1 (even though the literature says it isn't too critical). If you get it right you will have a cooler running engine, hence less chance of a piston seizure.     

I have also found that running-in a new engine needs to be taken very carefully and slow (not easy with modern traffic conditions, road ragers, etc etc).     

Sponge  

Avatar
nickjaxe
Runcorn Cheshire UK
Top Gear User
Club Member
Forum Posts: 2062
Member Since:
February 24, 2015
sp_UserOfflineSmall Offline
15
December 22, 2019 - 8:59 pm
sp_Permalink sp_Print

For me its throttle fully closed...part throttle with light load gives high combustion temps from the weak petrol/air mix so should be avoided..and every 30secs or so a quick blast of the throttle.

Of course just a short hill...just carry on.

We all have different ideas.

P.S. my idle mix is set slightly rich for this reason.

Nick.

My Bantam video              https://www.you.....jpOFmzRZRI

Forum Timezone: Europe/London

Most Users Ever Online: 223

Currently Online: Unitminor
27 Guest(s)

Currently Browsing this Page:
1 Guest(s)

Top Posters:

Cornish Rooster: 3314

cocorico: 3313

bart: 3130

Sprung Chicken: 2654

David Dale: 2485

Mags 1: 2356

Piquet: 2324

Blue Heeler: 2247

Munchkin: 2224

nickjaxe: 2062

Newest Members:

_2500

Forum Stats:

Groups: 9

Forums: 48

Topics: 12369

Posts: 106650

 

Member Stats:

Guest Posters: 1476

Members: 1450

Moderators: 0

Admins: 4

Administrators: Bantam-Super, JMD, Springs, Stoo63